The number of people killed in a series of deadly blasts that hit Sri Lanka on Sunday has risen to 359, Ada Derana news portal reported on Wednesday, citing police.

According to previous reports, 321 people were killed in the explosions.    

Police spokesman Ruwan Gunasekara has reportedly said Wednesday morning that 18 suspects were arrested overnight, raising the total detained to 58.

Sri Lanka's prime minister Ranil Wickremesinghe  warned on Tuesday that several suspects armed with explosives were still at large, according to Reuters.    

Earlier it was reported that around 500 people were wounded in the blasts, adding that 40 people were under arrest in connection with the attacks, which Sri Lanka's government has blamed on the local Islamist group National Thowheeth Jamaath.

Eight explosions took place in Sri Lanka on Easter Sunday; three churches and three hotels were targeted. Taken together, these constituted the worst attacks to have happened in the country's modern history, exceeding even the most notorious terror attacks of the country's 25-year civil war, which ended in 2009, in terms of civilian loss of life. 

A massive security operation was launched following the attacks. Sri Lanka's authorities introduced and re-introduced curfews, deploying an extra 1,000 troops in the capital Colombo.

Daesh* has reportedly claimed responsibility for the Sri Lanka attacks and released images that purported to show the attackers. Prime Minister Ranil Wickremesinghe said that investigators were still determining the extent of the bombers' foreign links, Reuters reported.