Sri Lanka's Catholic churches opened for Sunday worship again for the first time since suicide bombings killed hundreds over Easter.

St Sebastian Church in Negombo, where as many as 100 people were killed in the blasts, opened its doors to the public on Thursday. 

"It's been nearly three weeks. We lost our loved ones and our church was destroyed but our faith didn't die," the church said.

Churches were closed in the aftermath of the suicide bombings out of fear of more attacks. 

More than 250 people, including scores of children, were killed when suicide bombers attacked churches and luxury hotels on Easter Sunday. 

Authorities have put the blame on local radical Islamist groups, National Towheed Jamaat and Jammiyathul Millathu Ibrahim.

The Sri Lankan government says all of the suspects have either been apprehended or killed. 

Sri Lankan Catholic officials told the Associated Press that church-run schools closed since the attacks were due to be re-opened on Tuesday. 

Archbishop of Colombo Cardinal Malcolm Ranjith said it would be down to individual priests to determine whether it was safe to go ahead with mass on Sunday.

Security was tight outside Catholic churches that did hold mass, with armed police and military personnel patrolling the surrounding streets. 

Until now, worshippers have been meeting elsewhere or listening to mass livestreamed from a chapel at the residence of Archbishop Malcolm Ranjith. 

Zion Church and St Anthony's Church, which were also targeted, continue to meet in other venues as repairs are carried out on their buildings.