Eight blasts hit locations including churches and hotels across Sri Lanka, leaving at least 290 people dead and 500 injured
Congregations were taking part in Easter Sunday services at the churches when the blasts hit
The five-star Shangri-La, Kingsbury and Cinnamon Grand hotels in the heart of Colombo were targeted
A local group named as National Thowheed Jamath are believed to be behind the attack
Officials say 24 people have been arrested in connection with the attacks
Sri Lankan government clamps down on messaging services
Reuters is reporting that the Sri Lankan government has shut down access to major social media messaging services, though the BBC has received sporadic social media messages from people in Sri Lanka. It is unclear how far messaging services are affected.
Religious professor comments
BBC Radio 5 Live
Mathew Smaltz is a religious professor who has lived in Sri Lanka.
He told BBC Radio 5Live: "There was very little security presence at all and so it will it will curtail in many ways the ebb and flow of catholic life in Sri Lanka to the detriment of all.
"And so I think one of the questions will be how much adaptation the Catholic church is willing to make to these unprecedented events".
Sri Lanka's government has declared an islandwide curfew from 18:00 local time to 06:00 (12:30 GMT-00:30).
Eighth blast hits Colombo, reports say, locating it in the district of Dematagoda.
The seventh blast appears to have taken place at a smaller establishment altogether, in the suburb of Dehiwala. Reports so far suggest that two policemen were killed in that explosion.
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At least 67 people died at St Sebastian's church
Dan Wilcock, 31, from Leicester, is staying in Negombo for work.
His hotel is about a mile away from St Sebastian's church - which was severely damaged.
Images on social media showed its inside, with a shattered ceiling and blood on the pews. At least 67 people are reported to have died there.
He told the BBC: “I was surprised I could get so close to the church. You couldn’t see much - there were trucks outside and military.
"There quite a few upset people standing outside and every now and then the guards would let someone through."
Family from Surrey were staying at the Cinnamon Grand
Image source, ReutersThe Shangri La hotel was also targeted by bombers
Julian Emmanuel and his family, from Surrey, were staying at the Cinnamon Grand hotel in Colombo when the bomb went off.
He told the BBC: "We were in our room and heard a large explosion. It woke us up. There were ambulances, fire crews, police sirens.
“I came out of the room to see what’s happening, we were ushered downstairs.
“We were told there had been a bomb. Staff said some people were killed. One member of staff told me it was a suicide bomber...
“We were sent back to our rooms. We were reluctant to leave.
“I have family in Sri Lanka, I was born in Sri Lanka.
“We were supposed to have Easter brunch, but that’s on hold.
“We felt it’s safe to go out if we avoid big congregations, shopping malls, etcetera. Residential areas seem fine. Local restaurants, not hotel restaurants.
“They’re struggling here because they have lost a couple of kitchens, the bomb went off in the restaurant.”
Facebook has activated its crisis response in Sri Lanka, allowing people using the social media platform to let their friends and relatives know they are safe.
The blasts have triggered a wave of social media posts - mostly on Facebook and WhatsApp - with many images of the incident making the rounds.
Government officials - including the prime minister of the country - have urged people to refrain from spreading rumours and speculation on social media.
More reports now of that other blast in Dehiwala, a district in greater Colombo, - which our reporter has from the police who said it took place at a hotel opposite the zoo. AFP reports that two people were killed in that explosion.
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China's state news agency has reported that several Chinese nationals were injured in the explosion - but are now in a stable condition.
Another explosion has been reported in the district of Dehiwala, in greater Colombo. It is unclear what the nature of the explosion is as yet.
Imran Khan says Pakistan 'stands in complete solidarity' with Sri Lanka
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The Zion church, on Central Road, in the city of Batticaloa, is seen as one of the biggest churches in the eastern city.
The explosion hit the church in the morning as the Easter service was on.
The wider district of Batticaloa was caught up by Sri Lanka's civil war - it is majority Tamil, with Muslim and smaller Sinhalese populations there too.
The majority religion of the district is Hindu and Christians make up about 8% of the population, according to the 2012 census.
Image source, EPAAmerican ambassador to Sri Lanka tweets
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Sri Lanka is a majority Buddhist country, but also has a sizable population of Christians across its two major ethnic groups - Sinhalese and Tamils.
According to the 2012 census in the country, Christians - both Roman Catholic and other denominations - comprised 7.1% of the country's total population - or around 1.5 million people.
The Christian population has been targeted before this - with occasions when churches have either been stoned or set on fire, but never in this manner with this level of casualties.
Theresa May offers her 'deepest sympathies'
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Ex-pat brothers drove past hotels as bombs went off
Image source, John TylerThe Kingsbury hotel was one of three targeted
Image source, John TylerThe five star hotel is in the heart of Colombo
Image source, John TylerJohn Tyler, a visiting British ex-pat, took the photos shortly after the blast
British ex-pat John Tyler is in Colombo, visiting his brother Robert, who lives there.
The pair were going for a drive on the seafront, near the Kingsbury hotel, when the bombs went off.
John told the BBC: "We heard a bang or two, didn’t think much of it.
“Then we saw lots of people on their phones, ambulances.
“We got to the Kingsbury, saw the glass, thought it was an explosion in the kitchen".
Robert said they were about 500 metres from the Cinnamon Grand Hotel, which was also targeted.
"There was a bit of smoke", he said, adding: “We were just on our way for a coffee. We saw people outside of the Shangri-La Hotel on the lawn. Thought it could be a fire drill.
“A couple of connections I have, people I know here, have already gone to the airport".
He said the city was "really quiet" with talk of a possible curfew on Sunday night.
The attacks were well-planned and coordinated, though no group has said they carried out the blasts as yet.
The first blast was reported at St Anthony's, a hugely popular shrine in the centre of Colombo.
News then emerged of an explosion at St Sebastian's, a church in the town of Negombo, north of the capital and then a blast at the Zion Church in Batticaloa, in the east of the country.
Local media report that the timing of these blasts were near-simultaneous.
It was shortly afterwards that reports of blasts in the hotels were reported - but police are yet to issue exact timings.
Cardinal Archbishop of Colombo mourns loss of his people
BBC World Service
Image source, ReutersPriests outside St Anthony's church following the blast
Speaking to BBC World Service radio, Cardinal Archbishop of Colombo Malcolm Ranjith urged the people of Sri Lanka not to retaliate "because of hearsay", but to "wait patiently and work for peace and harmony".
He said it was a "very difficult and very sad situation for all of us because we never expected such a thing to happen and especially on Easter Sunday. Our people went to church without knowing anything. And then most of them were killed in those two churches".
The two churches of the three targeted - St Anthony's in Kochchikade and St Sebastian's Negombo - were huge attractions, he explained.
He said: "St Anthony’s church is a place frequented by people of practically all religions and it is therefore it’s a very vital centre in the city of Colombo.
"Then the other church in Negombo – which is called Little Rome because there are lots of Catholic churches in this town – and this is one of the main churches, the shrine church.
"So they have targeted on a day when many people will come to church and also the attendance will be very high.
"Really we didn’t have much of security in these churches because we never thought something like this would happen in one of our churches.
"I have already tried to go to St Anthony’s church but I was told not enter by the police because they were suspecting that there may be a second bomb. But I saw from outside that there had been a lot of structural damage but most of all the damage done to my people. This is a very sad thing indeed."
Ashitha NageshBBC News
Blood banks in Sri Lanka are now so overwhelmed with donors that staff are having to turn people away.
Usman Ali, a Colombo resident, tells the BBC that he went to the National Blood Centre to try and help the attack victims - and found a "huge crowd" of people spilling out of the building.
"Currently they are taking down the name, blood group and contact number of persons who are willing to donate blood, and asking them to return only if a representative of the National Blood Centre contacts them," he says.
"Everyone had just one intention and that was to help the victims of the blast, no matter what religion or race they may be. Each person was helping another out in filling [forms with] the details requested. I heard them speak in Sinhala, Tamil and English."
Image source, Usman Ali
Image source, Usman Ali