Nine explosions ripped through three churches holding Easter services on Sunday as well as four upmarket hotels in Sri Lanka leaving at least 290 people dead and 500 wounded.
Follow the latest developments as they happen here. All times UTC+4
22:00 Donald Trump speaks to Sri Lankan PM
US President Donald Trump had a phone call with the Sri Lankan prime minister to express his condolences.
"Spoke to Prime Minister Ranil Wickremesinghe of Sri Lanka this morning to inform him that the United States stands by him and his country in the fight against terrorism," Mr Trump said on Twitter.
"Also expressed condolences on behalf of myself and the people of the United States."
21:00 Spanish prime minister offers condolences for two citizens who died in the bombings
Spain’s Prime Minister, Pedro Sanchez, has offered his condolences after the deaths of two Spanish citizens in the bombings on Sunday.
"My love and solidarity to the friends and relatives of the two young people from Pontecesures who died in the Sri Lanka attacks," he tweeted. "Our heart is with all the victims of this cruel attack."
20:30 British father whose family died in the attack gives statement
British father Ben Nicholson has just given a statement on his wife Anita and two children Annabel, 11 and Alex, 14, who were killed in a bombing at the Shangri-La Hotel in Colombo while they were on holiday.
“I am deeply distressed at the loss of my wife and children. Anita was a wonderful, perfect wife and a brilliant, loving and inspirational mother to our two wonderful children," he said.
"The holiday we had just enjoyed was a testament to Anita’s enjoyment of travel and providing a rich and colourful life for our family, and especially our children.
“Alex and Annabel were the most amazing, intelligent, talented and thoughtful children and Anita and I were immensely proud of them both and looking forward to seeing them develop into adulthood.
"They shared with their mother the priceless ability to light up any room they entered and bring joy to the lives of all they came into contact with."
20:23 Authorities invoke military detain-and-interrogate measures
Sri Lanka said it was invoking emergency powers after the bomb attacks.
The emergency law, which gives police and the military extensive powers to detain and interrogate suspects without court orders, would go into effect at midnight local time, the president's office said.
Police said 87 bomb detonators were found at the city's main bus station, while an explosive went off near a church when bomb squad officials were trying to defuse it.
A curfew went into effect at 8pm local time.
17:25 Interpol called in to aid investigation
Interpol is sending a team of investigators, including experts in disaster victim identification, to Sri Lanka to help local authorities after the deadly bomb blasts, the international police organisation said.
The local government said it believed an Islamist extremist group named National Thowheeth Jama'ath was behind the attacks and would look at whether there was any international support for them.
Interpol said it was sending an Incident Response Team at the request of the Sri Lanka authorities, including specialists with expertise in crime-scene examination, explosives, counter-terror and victim identification.
17:05 US cancels Iran oil waivers, citing Sri Lanka blasts among reasons
US Secretary of State Mike Pompeo vowed that the Trump administration would keep fighting "radical Islamic terror" after the devastating attacks in Sri Lanka.
In a speech, he said sanctions waivers have not been renewed to eight countries importing oil from Iran, applying further economic pressure on Tehran to bring the country’s oil exports to zero.
"Radical Islamic terror remains a threat. We are continuing to do real work against these evil human beings," Mr Pompeo said.
"This is America's fight, too," he added, saying he had spoken by telephone with Prime Minister Ranil Wickremesinghe.
Iran is on the US's State Sponsors of Terrorism list.
14:40 Van explosion near Colombo church
A van blew up outside St Anthony's Shrine, one of the churches hit in Sunday's attacks, as a Sri Lankan bomb squad tried to defuse a device found inside the vehicle.
"The van exploded when the bomb defusing unit of the Special Task Force and air force tried to defuse the bomb," the witness said.
The National's Jack Moore reports:
A controlled explosion has taken place in the past half an hour about 50 metres away from St Anthony's Shrine in Colombo. Heavily equipped officers rushed to the scene before a bomb disposal unit moved in with a minesweeper.
A security cordon is in place to prevent anyone from getting near the scene. There are reports of a second device but this remains unconfirmed.
No injuries have been reported but it is clear that the threat is not over.
"There is a suspect issue in a small white minivan identified by the special task force, they have taken immediate actions. It was a controlled blast," a Ministry of Mega Police official told The National.
The National's Willy Lowry reports:
Meanwhile, police said they had found 87 bomb detonators at a bus station in Colombo.
A statement said officers found the detonators at the Bastian Mawatha Private bus stand, 12 of them scattered on the ground and another 75 in a garbage dump near by.
13:30 President set to declare a state of emergency
Sri Lankan President Maithripala Sirisena is set to declare a nationwide emergency from midnight on Monday after the Easter Sunday blasts.
The measure will grant police and the military extensive powers to detain and interrogate without court orders, and was in force at various times during the civil war with Tamil separatists.
Mr Sirisena will also ask for more foreign assistance in investigating the network behind the blasts, his office said.
"The intelligence reports indicate that foreign terrorist organisations are behind the local terrorists. Therefore, the president is to seek the assistance of the foreign countries," it said.
13:05 Attacks were assisted from overseas, says Sri Lankan Cabinet spokesman
Health Minister and Cabinet spokesman Rajitha Senaratne has pointed the finger at local extremist group National Thowheed Jama'ath for Sunday’s attack.
But Mr Senaratne said they were assisted by groups overseas.
"We do not believe these attacks were carried out by a group of people who were confined to this country," he said. "There was an international network without which these attacks could not have succeeded."
13:00 Sri Lanka declares Tuesday a day of mourning
12:56 British High Commission confirms eight nationals killed
The British High Commissioner to Sri Lanka says that eight British nationals were killed in yesterday's bomb attacks.
High Commissioner James Dauris said that the government had been in contact with Sri Lankan authorities and offered support in the continuing investigation.
12:55 Shangri-La Hotel closing until further notice
The Shangri-La Hotel will be closed until further notice, the hotel announced on Facebook.
It said that three employees had been killed in Sunday’s attack and that the hotel was working closely with local authorities and emergency services. The hotel, they said, “remains secured by the military and the police".
“Our immediate priority continues to be the safety and well-being of all affected,” it said.
12:50 Attacks carried out with help of international network says Sri Lankan cabinet spokesman
12:30 Children of billionaire clothing boss killed in Sri Lanka
Three children of Danish billionaire Anders Holch Povlsen were killed in Sunday’s attacks, his company confirmed on Monday.
The names of the children have not been disclosed but a spokesman for Mr Povlsen’s company, BestSeller, confirmed that the family had been in Sri Lanka on holiday at the time. Mr Povlsen has four children.
"Unfortunately, we can confirm the reports," a Bestseller spokesman told the BBC. "We ask you to respect the privacy of the family and we, therefore, have no further comments."
Mr Povlsen is the largest shareholder in online clothing giant Asos and The Times newspaper says he is Scotland's biggest landowner.
BestSeller owns Women’s brand Vero Moda as well as high street store Jack & Jones among others. The brands have outlets across Europe, the Middle East and is one of China’s largest European fashion companies with more than 1,200 stores.
12:00 Two Australians killed in bombings
The Australian Prime Minister, Scott Morrison, confirmed that two of the country's nationals were killed in one of the Sri Lankan bombings on Sunday. Another two were injured.
Mr Morrison said the two killed were from the same family and lived in Sri Lanka. One was a dual citizen. The two injured are in a stable condition. One is being treated for shrapnel wounds, while the other has a broken leg.
11:51 Sri Lankan government orders new curfew
The Sri Lankan government on Monday ordered a new night-time curfew as tensions remained high.
The curfew will run from 8pm until 4am on Tuesday.
An indefinite curfew after the attacks was lifted earlier on Monday, but a two-day holiday was decreed to reduce public traffic.
11:43 At the blood centre
The National's Willy Lowry visits a blood centre in Colombo.
"After the incident, many patients needed blood immediately. That's why I decided to donate my blood," says Sri Lankan Kamil Rajanayake.
11:15 At Colombo airport, locals and tourists remain defiant
The National's Jack Moore reports:
Colombo airport is full only hours after Sunday's attacks, despite it being the middle of the night.
People hurry inside the terminal building – everyone including police officers are searched – and are bustled through security.
In arrivals, a long queue of people stand waiting for airport taxis to be able to travel when the curfew is lifted at 6am.
Everyone is thinking about the massacre. Those arriving say they want to carry on with their holiday, while those working in the industry say there have been many cancellations.
"We are worried," says Dmitri, a 33-year-old from St Petersburg. "It is bad but we have to continue. We have paid money. It will be fine."
Saranga, 40, is an employee of the Cinnamon Grand, the first hotel to be hit on Sunday.
"We have no words. We don't know how people can do these things. These people are crazy, they have lost their minds," he said.
Saranga says the hotel is still open, albeit partially, and says some people still plan to stay.
Full story on the mood inside Bandaranaike International
10:10 Church and hotel attacks were suicide bombings
Sri Lankan government forensic analyst says that the six church and hotel bombings on Sunday were carried out by seven suicide bombers.
Reports indicate that all the sites were hit by a single bomber, except the Shangri-La hotel which was hit by two. There is no indication of why that target appears to have been hit twice.
10:10 US warns of further plots
The US has revised its travel advisory for Sri Lanka, warning that “terrorist groups” are continuing to plan attacks, just a day after 290 people were killed and 500 wounded in near-simultaneous blasts in churches and luxury hotels on Easter Sunday.
The State Department travel advice for Sri Lanka said: “Terrorists may attack with little or no warning."
It said possible targets included tourist locations, transport centres, shopping malls, hotels, places of worship and other public areas.
Several countries have revised their travel advice for Sri Lanka after Sunday’s attack.
10:02 The National on the ground in Colombo
The National's Jack Moore and Willy Lowry are reporting from Colombo after the deadly attacks on Easter Sunday.
Lowry captures the eerie scenes of silence in Colombo during the curfew.
10:00 Is it safe to travel to Sri Lanka?
The UAE Ministry of Foreign Affairs and International Co-operation has issued a travel warning, advising Emirati citizens to postpone travel plans due to the security situation.
Other countries have also issued warnings with Australia's Department of Foreign Affairs and Trade urging people to officially reconsider their need to travel.
In the US, Sri Lanka has been listed at a Level 2, which means travellers should exercise increased caution.
09:45 Air Force defused pipe bomb near airport
A Sri Lanka military spokesman said that an explosive device was found and defused late on Easter Sunday on an access road to the international airport near Colombo.
Air Force Group Captain Gihan Seneviratne said on Monday that authorities found a "homemade" pipe bomb filled with 50 kilograms of explosives Sunday night in Andiambalama, near the airport.
09:45 'There was a river of blood'
Here's our full report of how events unfolded on Sunday
09:40 Mother-of-two from Dubai killed in attacks
A mother-of-two from Dubai is understood to have been killed in one of the devastating bomb blasts that shook Sri Lanka early on Sunday, The National's Liz Cookman reports.
Razeena Kukkady, 58, is thought to have been enjoying breakfast in the Shangri-La Hotel in Colombo when the attackers struck.
Relatives described her as a keen traveller and a "fantastic cook" who was always ready to help others.
Born in India, she grew up in Sri Lanka but later moved to Jumeriah Lake Towers in Dubai with her husband.
09:33 Five Indians killed in attacks
Indian officials say five Indians were killed in the bombings.
The external affairs minister and the Indian High Commission in Sri Lanka identified the five victims in a series of tweets.
Indian Prime Minister Narendra Modi also spoke to Sri Lankan leaders and condemned the blasts. On Sunday, Mr Modi tweeted:
Sri Lankan authorities have said at least 27 of the more than 200 dead were foreigners.
The US said several were Americans but didn't give a figure. Japan has confirmed one dead. Sri Lanka's Foreign Ministry said one Portuguese, two Turkish nationals, three British nationals and two dual US-British nationals were among those killed.
09:15 Sri Lanka lifts curferw
No-one has claimed responsibility for the attacks on two churches and four hotels in and around Colombo and a third church on the country's north-east coast.
A government source said President Maithripala Sirisena, who was abroad when the attacks happened, had called a meeting of the National Security Council early on Monday.
Prime Minister Ranil Wickremesinghe would attend the meeting, the source said.
09:00 Police to examine intelligence failings
Sri Lankan Police said the investigation into the Easter Sunday bombings would examine reports that the intelligence community failed to detect or warn of possible suicide attacks before the violence.
Two government ministers have alluded to intelligence failures.
Telecommunications Minister Harin Fernando tweeted:
And Mano Ganeshan, the Minister for National Integration, said the security officers within his ministry had been warned by their division about the possibility that two suicide bombers would target politicians.
How the attacks unfolded on Easter Sunday
The churches were full on Sunday morning as Christians in Sri Lanka gathered for one of the most important religious holidays of the year.
But what unfolded next would shake the nation and shock the world.
A little before 9am, suicide bombers detonated explosives at three churches across the country. Within minutes, scores were dead and hundreds wounded.