Turkish officials across the political spectrum have condemned a shooting that killed one person at a Catholic church in Istanbul on Sunday.
ISIS claimed responsibility for the attack, with two militants fleeing the scene, the group said.
The deadly assault was in response to a call by the group's leaders to attack Jews and Christians, the militants said.
Interior Minister Ali Yerlikaya said Turkish authorities later captured the two gunmen.
Authorities carried out raids on more than 30 locations across Istanbul and detained 47 people, Mr Yerlikaya told media.
The suspects were captured in one of the last raids, he said.
"Both of the suspects are foreign nationals," Mr Yerlikaya said.
He said they would be questioned about the attack.
"One of them is from Tajikistan and the other is Russian, and we evaluated them to be with [ISIS]," Mr Yerlikaya said.
Several people were injured during the shooting, officials said, identifying the victim only by the initials “CT.”
“Any attack on a single human being, let alone our Christian citizens, is treason,” Cemal Enginyurt, an Istanbul MP from the opposition Democrat Party, told The National.
Turkey is a Muslim-majority country, and although freedom of belief is guaranteed in the constitution, the country's Christian population has decreased over the decades to a couple of hundred thousand people, according to the US State Department's most recent report on religious freedom.
After Sunday's attack, members of the clergy in the city of Izmir demanded that "greater security be guaranteed for our communities and churches".
A Catholic priest in the city told The National that Turkish Christians must exercise care, but community leaders still believe in religious co-existence in the country.
"We Christians, here as in many parts of the world, must be cautious," said Fr Alessandro Amprino.
"But nothing, including terrible gestures like this, will be capable of destroying our commitment to building dialogue between different religions and cultures."
Attacks on Christians in Turkey are not without precedent. In 2007, five assailants entered a Christian publishing office in the south-eastern Malatya province and killed three people.
Pope Francis expressed his support for Istanbul's Christians during an address at the Vatican on Sunday.
"I express my closeness to the community of the Santa Maria Draperis Church in Istanbul," the Pope said.
Italian Foreign Minister Antonio Tajani also condemned the "cowardly" attack, adding that Rome is following up with its diplomatic representatives in Turkey.
The British government updated its travel advice after the shooting, instructing its citizens in the area to “remain vigilant”.
The attack comes as Turkish political parties prepare for local elections on March 31, in which district and provincial level leaders will be elected.
Istanbul’s mayorship will be fiercely contested, with President Recep Tayyip Erdogan’s Justice and Development Party (AKP) hoping to regain control of Turkey’s largest city from the opposition Republican People's Party (CHP).
"We will never allow those who try to destroy our unity and peace by attacking the religious places of our city," said Istanbul Mayor Ekrem Imamoglu.
His opponent from the AKP, Murat Kurum, said: “These vile attacks, which target our centuries-old law of brotherhood and our will to live together, will never reach their target."
AKP spokesman Omer Celik said security forces "are conducting a large-scale investigation into the matter".
“Those who threaten the peace and security of our citizens will never achieve their goals,” he said.
Turkey's broadcasting authority later imposed a reporting ban on the incident, a move often made after terror attacks in the country.
In a post on social media, Sariyer district mayor Sukru Genc described the incident as a “terrorist act”.
Opposition politicians criticised authorities’ response to the attack, and said that hazy information about what happened increased levels of doubt and fear among citizens.
There is “no accurate information about the deceased or injured. This is not only pathetic but terrifying,” Unal Cevikoz, a former Turkish diplomat and CHP MP for Istanbul, told The National.
“A blackout like that creates suspicion and nobody can be sure about the validity of official statements.”
In response to the attack, Turkish politicians are likely to show a tough stance on crime and possible acts of terrorism, while also aiming to show Turkey’s plurality and tolerance of religious diversity.
Authorities have faced criticism in recent years for increasingly conservative Islamist trends.
“Attacking places of worship and people worshiping is the lowest level of humanity. Those who committed this tragic incident will be held accountable before the law,” Istanbul MP Ozlem Zengin, of the AKP, told The National.
“In Turkey, people from all religions live side by side in peace and worship freely.”
Sariyer was in Mr Cevikoz’s former constituency when he was a CHP MP, and the area’s non-Muslim community was “always very peaceful”, he said.
“I have been to the church several times during my election campaign in 2018 and used to know many people from the community.”
Turkey’s religious minorities are concentrated in Istanbul and other large cities.
There are no exact statistics, but the latest US State Department report on religious freedom in Turkey says there are nearly 100,000 Armenian Apostolic Orthodox Christians and 25,000 Roman Catholics in the country, as well as 25,000 Syrian Orthodox Christians and up to 16,000 Jews.
Tens of thousands of Russians and Ukrainians who have migrated to Turkey since Russia’s February 2022 invasion of Ukraine have boosted numbers of Eastern Orthodox Christians to about 150,000.
Some officials said the attack may be an attempt to disrupt security before the March vote.
“Many unfortunately think that this is happening because of the approaching elections on 31st March and that the Christian community is being threatened,” Mr Cevikoz said.
“Now that such an unprecedented attack has happened, I believe the security measures around the churches and synagogues in Istanbul, and all over Turkey, will be strengthened and a recurrence of such a terrorist attack will hopefully be deterred.”
In December, Turkish security forces detained 32 suspects, allegedly linked with ISIS, and accused of planning attacks on churches, synagogues and the Iraqi embassy.
About 500 people were killed in a campaign of terror attacks from 2015 to 2017 that hit major cities, including Istanbul and Ankara.
The bombings were mostly attributed to ISIS and Kurdish militants from the outlawed Kurdistan Worker's Party (PKK).
Six people were killed in the most recent attack on Istanbul's busy Istiklal Avenue in November 2022.
In 2017, an attack on an Istanbul nightclub left 39 people dead.