Sri Lanka's Christians on Sunday honoured the 279 people killed in the 2019 Easter bombings as the island's top Catholic leader warned of street protests unless those responsible were prosecuted.

Cardinal Malcolm Ranjith lit candles at the St. Anthony's church where 56 people perished when local jihadists carried out coordinated suicide attacks against three hotels and three churches.

The Christian minority across the country attended Easter Sunday masses under tight armed police and military security amid fears of fresh attacks, officials said.

Ranjith renewed his call for swift action against those responsible for the attack and said the then president Maithripala Sirisena should be prosecuted for criminal negligence in failing to prevent it.

Security has been stepped up at churches across Sri Lanka ahead of Easter Sunday services
Security has been stepped up at churches across Sri Lanka ahead of Easter Sunday services AFP / Lakruwan WANNIARACHCHI

An investigation ordered by Sirisena soon after the April 21, 2019, bombings found that he and his intelligence officials had precise information from India about the impending attack 17 days earlier, but failed to act.

"President Sirisena's guilt has been identified in the commission report," Ranjith told reporters outside the St. Anthony's church. "I ask President Gotabaya Rajapaksa and his government why they are dragging their feet without prosecuting him."

"We will take to the streets if no action is taken by April 21," Ranjith said.

Rajapaksa came to power in November 2019 promising action against those responsible for the 2019 attack. Sirisena who did not offer himself for re-election is currently a legislator from Rajapaksa's SLPP party.

Security has been stepped up at churches across Sri Lanka ahead of Easter Sunday services
Security has been stepped up at churches across Sri Lanka ahead of Easter Sunday services AFP / Lakruwan WANNIARACHCHI

Christians observed a two-minute silence from 8.45 am (3.15 GMT) when the first of seven bombers struck in the coordinated attacks. Each target had one bomber while at the Shangri-La hotel there were two suicide bombers.

Security was stepped up at churches across the Buddhist-majority country ahead of Easter Sunday services to guard against a repeat of the suicide bombings blamed on a local jihadist group.

Police spokesman Ajith Rohana said more than 12,500 armed constables were on duty outside 1,944 churches, and were backed by military personnel.

"We have also got the help the armed forces to patrol and reinforce police units across the country," Rohana said.

Sri Lanka was shaken on Easter Sunday in 2019 when jihadists staged the largest single terror attack in the history of the country. The attack came 10 years after the end of its 37-year Tamil separatist war.

At least 279 people, including 45 foreign nationals, were killed in the attacks, and around 500 were wounded.

Police checked identity cards and bags before allowing people to attend the morning mass at St. Sebastian's church north of the capital Colombo, where 115, including 37 children, were killed in the Easter attack.

The names of the victims were read out after the morning mass and candles lit and flowers placed at graves near the church.

More than 200 people have been arrested in connection with the bombings, but no one has been indicted yet.

Posters calling for justice were put up outside St. Sebastian's, which was packed with worshippers on Sunday despite the strict social distancing regulations in place due to the Covid-19 pandemic.