Sri Lankan President Maithripala Sirisena said on Friday police are looking for 140 people believed to have links with the militant Islamic State (IS) group, which has claimed responsibility for the Easter Sunday suicide bombings of churches and hotels.

Muslims in Sri Lanka were urged to pray at home on Friday and not attend mosques or churches after the State Intelligence Services warned of possible car bomb attacks, amid fears of retaliatory violence for the bombings that killed 253 people.

The United States embassy in Sri Lanka also urged its citizens to avoid places of worship over the coming weekend after authorities reported there could be more attacks targeting religious centres.

Sri Lanka remains on edge after the suicide bombing attacks on three churches and four hotels that also wounded about 500 people.

Nearly 10,000 soldiers were being deployed across the Indian Ocean island state to carry out searches and provide security for religious centres, the military said on Friday.

Fears of retaliatory sectarian violence have already caused Muslim communities to flee their homes amid bomb scares, lockdowns and security sweeps.

The All Ceylon Jamiyathul Ullama — Sri Lanka's main Islamic religious body, urged Muslims to conduct prayers at home on Friday in case “there is a need to protect family and properties”.

Cardinal Malcolm Ranjith also appealed to priests not to conduct mass at churches until further notice.

“Security is important,” he said.

Police have detained at least 76 people, including foreigners from Syria and Egypt, in their investigations so far. The IS provided no evidence to back its claim that it was behind the attacks. If true, it would be one of the worst attacks carried out by the group outside Iraq and Syria.

The extremist group released a video on Tuesday showing eight men, all but one with their faces covered, standing under a black IS flag and declaring their loyalty to its leader, Abu Bakr Al-Baghdadi.