An extremist leader considered a central figure in Sri Lanka's Easter suicide bombings died in the attacks, the president says as the police chief became the latest figure to quit over the failure to prevent the massacre.

Sri Lankan officials revise the death toll from Easter Sunday bombings down by about 100 on Thursday, blaming the difficulty in identifying body parts at bomb scenes for the earlier inaccurate number.

As mourners buried the remains of Christian worshippers killed by the Easter Sunday suicide bomb attacks in Sri Lanka, hundreds of Muslim refugees fled Negombo on the country's west coast where communal tensions have flared in recent days.

Sri Lankan President Maithripala Sirisena has asked the police chief and defence secretary to quit following the Easter Sunday suicide bomb attacks on churches and luxury hotels that killed 359 people, two sources close to the president have said.

Chilling CCTV footage has emerged showing a suicide bomber calmly patting a child on the head and shoulder moments before he walked into a packed Sri Lankan church, unleashing carnage.

The scale and sophistication of the Easter Sunday attacks on churches and hotels in Sri Lanka suggested the involvement of an external group such as Islamic State, the US ambassador says as the death toll jumped to 359.

Standing under a black flag of the Islamic State, eight men declare their loyalty to the group's leader, Abu Bakr Al-Baghdadi. "We pledge allegiance ... and to obey him on everything either in easy or difficult conditions," they say, before praising Allah.

Senior officials deliberately withheld intelligence about possible attacks on Sri Lanka, where a rash of suicide bombings on Easter Sunday killed at least 359 people, the leader of Sri Lankan parliament says.

Sri Lankan police says they had detained 18 more people for questioning over the Easter Sunday attacks on churches and hotels, claimed by the Islamic State group, as the death toll climbed again to 359.

China yesterday warned that the US decision to impose sanctions on buyers of Iranian oil will “intensify turmoil” in the Middle East and in the international energy market.

Muslim brothers carried out two of the hotel suicide blasts in Sri Lanka on Easter Sunday, part of a wave of bombings that killed more than 320 people, police sources tell AFP.

Moshiul Haque Chowdhary, son-in-law of Awami League Presidium Member Sheikh Fazlul Karim Selim, has been taken to ICU of a hospital in Sri Lanka after surgeries.

Sri Lankan police are holding a Syrian national in custody for questioning over the Easter Sunday attacks on churches and hotels, three government and military sources tell Reuters.

Rescuers dig into rubble to reach people trapped in a supermarket that collapsed in Porac town, Pampanga province, after a 6.1-magnitude earthquake shook Luzon.

Sri Lankan President Maithripala Sirisena will declare a nationwide emergency from midnight on Monday following Easter Sunday suicide bomb blasts at churches and luxury hotels that killed 290 people and wounded more than 500, his office says..

Authorities lift a curfew in Sri Lanka today, a day after a string of bombings at churches and luxury hotels across the Indian Ocean island killed 290 people and wounded about 500, but there are warnings more attacks were possible.

As Shantha Prasad carries children wounded in Sri Lanka's deadly attacks into a Colombo hospital, memories of the country's deadly civil war floods back. For many Sri Lankans, Sunday's attacks against churches and high-end hotels brings back painful memories of the conflict that lasted three decades and killed as many as 100,000 people.

When Dilip Fernando arrived at St Sebastian's church in Sri Lanka's Negombo on Easter Sunday, it was so crowded he went elsewhere for mass. The decision probably saved his life.

As many as 36 foreigners have been killed and nine reported missing following Easter Sunday attacks in different parts of Sri Lanka.

An improvised pipe bomb discovered close to Colombo's main airport was successfully defused by the Sri Lanka airforce, police say.