A string of eight powerful blasts, including suicide attacks, struck churches and luxury hotels frequented by foreigners in Sri Lanka on Easter Sunday, killing 215 people, including three Indians, and shattering a decade of peace in the island nation since the end of the brutal civil war with the LTTE.

The blasts - one of the deadliest attacks in the country's history - targeted St Anthony's Church in Colombo, St Sebastian's Church in the western coastal town of Negombo and Zion Church in the eastern town of Batticaloa around 8.45 a.M. (local time) as the Easter Sunday mass were in progress, police spokesman Ruwan Gunasekera said.

Explosions were reported from three five-star hotels - the Shangri-La, the Cinnamon Grand and the Kingsbury in Colombo.

Gunasekera confirmed 207 deaths. However, the News 1st channel said that 215 people have died in the blasts.

Chairman of Sri Lanka Tourism Kishu Gomes said 33 foreign nationals have been killed in the coordinated attacks believed to be carried out by a single group. Director of the National Hospital Dr Anil Jasinghe identified 12 of the 33 foreign nationals, which include three Indians, two Chinese and one each from Poland, Denmark, Japan, Pakistan, America, Morocco and Bangladesh.

External Affairs Minister Sushma Swaraj, in a series of tweets, identified the three Indians as Lakshmi, Narayan Chandrashekhar and Ramesh.

"Indian High Commission in Colombo has conveyed that National Hospital has informed them about the death of three Indian nationals," she said in a tweet.

Around 500 people, including Indians, were injured in the attacks.

No group has claimed responsibility for Sunday's attacks.

Briefing reporters, Gunasekera said the police was not able to confirm at the moment if they were all suicide attacks. He, however, said that one of the blasts at the Katuwapitiya (Negombo) church has signs of being what looked like a suicide attack.

An unnamed official said a suicide bomber blew himself up at the restaurant of the Cinnamon Grand hotel.

Gunasekara said that 66 bodies were kept at the National Hospital while 260 injured were receiving treatment there and 104 bodies were placed at the Negombo Hospital and 100 injured were receiving treatment at the Hospital.

Later in the day, a powerful blast in the capital's southern suburb near the Colombo Zoo killed two persons, Gunasekera said.

When a police team entered a house in the Colombo north suburb of Orugodawatta to conduct a search, a suicide bomber blew himself up causing a concrete floor of a two-storey building to crash on them, killing three policemen in the eighth blast, police said.

Soon after the eighth blast, the government imposed curfew with immediate effect. The curfew will be in force indefinitely until further notice, officials said.

Gunasekera said 13 suspects have been arrested.

State Minister of Defence Ruwan Wijewardene said "We believe these were coordinated attacks, and one group was behind them".

President Maithripala Sirisena has appealed for calm.

"I have been shocked by this totally unexpected incidents. The security forces haven been asked to take all action necessary," Sirisena said.

Prime Minister Ranil Wickremesinghe termed the blasts as "cowardly attacks" and said his government was working to "contain the situation."

Late in the evening, he said "the government was aware of the information regarding a possible attack but adequate precautions were not taken to prevent it".

He also said that as per the information he has received, "the perpetrators were locals".

Security has been intensified around the religious places across the capital. The government has temporarily blocked all social media platforms.

"Horrible scenes. I saw many body parts strewn all over," said Harsha de Silva, Sri Lanka's Minister of Economic Reforms and Public Distribution.

The Indian High Commission in Colombo said that it was closely monitoring the situation in Sri Lanka.

The first blasts were reported at St Anthony's church in Colombo and St Sebastian's Church in Negombo just outside the capital.

Images circulated on social media showed severely damaged St Sebastian's church, with a shattered ceiling and blood on the pews.

The riot police and the Special Task Force, extra police security has been deployed around the Bandaranaike International Airport, state-run Daily News reported.

All state Universities have been closed until further notice.

Cardinal Malcolm Ranjith said all Easter masses in the Colombo District have been cancelled.

Former president Mahinda Rajapaksa, under whose leadership the Lankan Army crushed the LTTE, termed the attack as "barbaric".

Christianity is a minority religion in Sri Lanka, where the majority are Buddhists. Christians account for less than 10 per cent of the total population of 21.4 million.

Sunday's attacks are the deadliest seen in Sri Lanka since the end of the country's civil war in 2009. The civil war ended with the defeat of the Tamil Tigers, who had fought for 26 years for an independent homeland for the minority ethnic Tamils. The war is thought to have killed between 70,000 and 80,000 people.

The nation has seen some sporadic violence since. In March 2018, a state of emergency was declared after members of the majority Buddhist Sinhala community attacked mosques and Muslim-owned properties.