Two people have been killed after a man attacked people on London Bridge with a knife in an incident being treated as terrorism.
The suspect was a former prisoner with a terror conviction.
Armed officers shot dead the man who was wearing a hoax bomb vest.
The suspect was apprehended by members of the public who selflessly put their own lives at risk to pull the weapon from him while not realising that the bomb vest strapped to his chest was a fake.
Police said the two dead members of the public were a man and a woman. Two women and a man were also injured and remain in hospital.
Metropolitan Police chief Cressida Dick said officers were called just before 2pm local time to Fishmongers’ Hall, a conference venue at the north end of London Bridge. The pedestrian and vehicle bridge links the city’s business district with the south bank of the River Thames, was reported about 2pm.
Cambridge-based prison-education organisation Learning Together was holding an event there on Friday. The University of Cambridge said it was “gravely concerned” about students, staff and alumni who might have been caught up in the attack.
The suspect, who attended the event, was named by police as 28-year-old Usman Khan.
"This individual was known to authorities, having been convicted in 2012 for terrorism offences," Britain's top counter-terrorism police officer, Neil Basu, said in a statement.
"He was released from prison in December 2018 on licence and clearly, a key line of enquiry now is to establish how he came to carry out this attack," Mr Basu said.
Soon after the interventions of the people on the central London bridge, the armed officers arrived at the scene of the attack and shot the man, killing him instantly.
Prime Minister Boris Johnson praised the heroics of the pedestrians of everyone involved.
"I want to pay tribute to the extraordinary bravery members of the public who physically intervened to protect the lives of others. For me, they represent the very best of our country and I thank them on behalf of all of our country," Mr Johnson said.
"I think the message we send to them and anyone associated with this type of attack is one that will be familiar and that is this country will never be cowed, or divided or intimidated by this sort of attack and our British values will prevail," he added.
There is likely to be a meeting of the government’s COBRA emergencies committee on Saturday.
The major political parties agreed to put on hold campaigning for the UK general election.
The incident happened on Friday when police were called at lunchtime to a stabbing at premises near to the iconic Monument landmark north of the bridge.
Terrified witnesses had described a man with a large knife attacking people.
Kevin O’Rourke, a security guard at Nomura International bank, told reporters that he watched terrified bus passengers fleeing from a man carrying a large knife.
“One of our clients said he saw a man with a big machete knife. Everybody was running away. It was absolutely terrifying for them," he said.
“Apparently there was a fight on the bridge with two people stabbed. Then at one point I heard about 10 or 12 gunshots, pop, pop, pop."
Mr Basu confirmed the police killed the man at the scene.
“A male suspect was shot and I can confirm the suspect died at the scene," he said.
“We believe a device that was strapped to the body of the suspect was a hoax device.
“Officers from the counter terrorism command are now leading this investigation.”
Footage of the pedestrians restraining a man and retrieving a weapon from him was widely shared on social media. It shows the police pulling them to safety before shooting the assailant.
The Metropolitan Police said five people were stabbed on a premises before the man went to the bridge.
Counter-terrorism police have been drafted into the area and roads have been cordoned off.
Noa Boder, who was trapped in a restaurant next to London Bridge, described a "rush of people" coming into the venue, adding "everybody basically dived under the table".
"We were told to keep away from the windows."
She says the manager of the restaurant "very bravely" ran and shut the doors to make sure nobody could come in.
"Everybody seems to be calm and in good spirits here and asking if people are OK," she added.
Another onlooker named Joe, who was in a building nearby, told LBC radio station: "We saw loads of police cars heading towards the bridge and then we saw a man on the ground and police pointing guns at him.
“We were ushered away from the windows and when we returned to the window there was a woman being carried away from the scene.”
Reem Youssef added: “I heard shouting and I looked up and saw potentially four or five people having a fight and shouts get back, back. I then heard gunshots.”
London mayor Sadiq Khan Khan urged the city to remain "resolute".
In a statement on Friday he said: "We must stay resolute in our determination to stand strong and united in the face of terror.
"Those who seek to attack us and divide us will never succeed."
High security is in place across the UK capital ahead of the NATO summit next week.
The terror attack comes just two years after London Bridge was the scene of an ISIS attack in 2017 which left eight people dead and 48 people injured.
It saw three men drive a van into pedestrians on the bridge, before disembarking and running into nearby Borough Market where they began stabbing members of the public with 12-inch blades.
The three attackers were shot dead by police and were found to be wearing fake suicide vests.
The government has yet to announce if it will be raising the UK’s terror threat level from substantial to severe.
Extra police have been drafted into the London from surrounding areas to help deal with the incident.
Following the previous attack, Mr Khan reported a “significant spike in incidents of hate crime and Islamophobic incidents” in the aftermath.
The ISIS-inspired attack prompted a recommendation that the UK’s domestic intelligence agency, MI5, should strengthen its investigations into terror suspects.
Earlier this month the chief coroner for England and Wales said new laws should be introduced to tackle the possession of extremist propaganda.