At least 207 people have been killed and hundreds more injured in explosions at churches and hotels in Sri Lanka, police and hospital sources say.
At least eight blasts - many of them from suicide bombers - were reported.
Three churches in Negombo, Batticaloa and Colombo's Kochchikade district were targeted during Easter services.
The Shangri-La, Kingsbury, Cinnamon Grand and a fourth hotel, all in Colombo, were also hit.
A curfew has been imposed from 18:00 to 06:00 local time.
No group has yet said it was responsible.
Images on social media showed the inside of one of the churches - St Sebastian's in Katuwapitiya - with a shattered ceiling and blood on the pews. At least 67 people are reported to have died there.
There were heavy casualties too at St Anthony's Shrine in Kochchikade, a district of Colombo.
Among those killed in Colombo were at least 27 foreign nationals - including two Turks and a Dutch person - and another five visitors are missing, the BBC reports.
Hospital sources in Batticaloa said at least 27 people had died there.
A hotel official at the Cinnamon Grand, near the prime minister's official residence, told Agence France-Presse the explosion there had ripped through a restaurant, killing at least one person.
Colombo resident Usman Ali told the BBC there were massive queues as he joined people trying to donate blood.
He said: "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."
Overwhelming response at National Blood Centre. It’s so overcrowded they cannot control the crowd. Currently they are sending back people who have come after taking down name, contact and blood group. Don’t rush there now go leisurely as the crowd subsides #LKA pic.twitter.com/EAvYyr73kH— Usman Ali (@usmanali_la) April 21, 2019
What have officials said?
President Maithripala Sirisena has issued a statement calling for people to remain calm and support the authorities in their investigations.
PM Ranil Wickremesinghe is chairing an emergency meeting. He said: "I strongly condemn the cowardly attacks on our people today. I call upon all Sri Lankans during this tragic time to remain united and strong."
On Twitter, Finance Minister Mangala Samaraweera said the attacks appeared to be a "well-co-ordinated attempt to create murder, mayhem and anarchy" and had killed "many innocent people".
Another minister, Harsha de Silva, described "horrible scenes" at St Anthony's Shrine in Kochchikade, saying he had seen "many body parts strewn all over".
No-one has yet said they were responsible for the attacks.
There have been fears that returning fighters from the Islamic State group could pose a threat in the country.
In the years since the end of Sri Lanka's civil war, there has been some sporadic violence, with members of the majority Buddhist Sinhala community attacking mosques and Muslim-owned properties. That led to a state of emergency being declared in March 2018.
Ardern extends condolences
The Prime Minister Jacinda Ardern has extended New Zealand's condolences to the government and people of Sri Lanka following multiple bombings there today, Easter Sunday.
She said New Zealand condemns all acts of terrorism, and its resolve has only been strengthened by the attacks in Christchurch on 15 March.
Ms Ardern said to see an attack in Sri Lanka while people were in churches and at hotels is devastating.
New Zealand rejects all forms of extremism and stands for freedom of religion and the right to worship safely, she said.
At least 115 New Zealanders are currently in Sri Lanka and New Zealand's Ministry of Foreign Affairs and Trade says they are responding to the incidents.
They advise New Zealanders travelling in Sri Lanka to be extremely cautious and vigilant in public areas, follow safety advice being given by local authorities, and register their presence on their website.
- BBC / RNZ