Around 130 people have been killed in a series of Easter Sunday explosions targeting three churches and three hotels in Sri Lanka.
The blasts took place in Colombo, in the south of the country, and local officials say at least 138 people were killed.
More than 500 people have also been injured.
Two of the blasts were suspected to have been carried out by suicide bombers.
St Anthony's Shrine and the Cinnamon Grand, Shangri-La and Kingsbury hotels are the locations where the blasts took place.
Other blasts were reported at St Sebastian's Church in Negombo, a majority Catholic town north of Colombo, and at Zion Church in the eastern town of Batticaloa.
St Sebastian's appealed for help on its Facebook page.
The explosion ripped off the roof and knocked out doors and windows at St Sebastian's, where people carried the wounded away from blood-stained pews, local TV footage showed.
Sri Lankan security officials said they were investigating. Police immediately sealed off the areas.
Prime Minister Ranil Wickremesinghe has convened Sri Lanka's top military officials at an emergency meeting of the National Security Council following the blasts.
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Turkish President Recep Tayyip Erdogan condemned the attacks, calling them "an assault on all of humanity."
In the UK, Prime Minister Theresa May said "no one should ever have to practise their faith in fear" following blasts which tore through three churches and three hotels.
Mrs May added: "The acts of violence against churches and hotels in Sri Lanka are truly appalling, and my deepest sympathies go out to all of those affected at this tragic time.
"We must stand together to make sure that no one should ever have to practise their faith in fear."
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Meanwhile, Labour leader Jeremy Corbyn said: "I'm appalled by the horrific attacks in Sri Lanka, on Easter Sunday, the most important day in the Christian calendar.
"I stand with the victims, their families, the people of Sri Lanka and Christians around the world. We must defeat this hatred with unity, love and respect."
A spokesman for the Foreign and Commonwealth Office said: "We are aware of reports of a number of explosions in Sri Lanka, including Colombo, and we are urgently seeking information from the local authorities.
"British nationals in Sri Lanka should follow the instructions of the local authorities and check FCO travel advice for updates."
