The bombings killed 257 people and wounded hundreds at three churches and three hotels

Two bomb experts were among the suicide attackers who struck churches and hotels on Easter in Sri Lanka and all those directly involved in the bombings are either dead or under arrest, police said.

Acting police chief CD Wickramaratne said in a statement late on Monday that explosives the Islamic State-linked group stacked for use in more attacks have been seized.

The bombings killed 257 people and wounded hundreds at three churches and three hotels. Seven suicide bombers died at their targets while another exploded his device later at a guesthouse after his device failed at a leading tourist hotel. A ninth killed herself to avoid capture by police at her home.

Police have detained 73 suspects for investigations since the bombings and have seized stocks of explosives, improvised explosives devices and hundreds of swords. They have also found $140,000 in cash in bank accounts connected to the group and another $40 million worth of assets in land, houses, vehicles and jewellery.

Authorities had repeatedly said another attack from the extremist group was possible.

Sri Lanka's Catholic church hierarchy closed churches for a second weekend on Sunday as the faithful celebrated Mass from home watching live on television.

On Tuesday, one of the churches targeted in the attacks, St. Anthony's Shrine in Colombo, opened a section of the church to the public for the first time since the bombing, enabling devotees to pray in the church as was customary every Tuesday.

Catholic schools remain closed until further notice after reports said two of their locations were to be attacked last weekend.

Government-run schools reopened for students of higher classes Monday but fewer students attended out of fear.

Army Commander Mahesh Senanayake on Monday urged the public to resume normal activities trusting in the security forces.

"I ask the people not to fear unnecessarily, not to believe rumours...believe in the tri-forces and police that defeated one of deadliest terrorist organisations in the world," he said of the ethnic Tamil separatists who fought a 26-year civil war. The conflict ended 10 years ago.