The Islamic State group on Tuesday said it was behind a devastating string of suicide attacks against churches and hotels in Sri Lanka that killed more than 320 people on Easter Sunday.  

(Photo: AFP)

The claim emerged more than 48 hours after the near-simultaneous blasts tore through three high-end hotels popular with foreigners and three churches packed with Christians marking Easter.

It came after Sri Lanka's government said initial investigations suggested the attack had been carried out as "retaliation" for shootings at two mosques in New Zealand last month that killed 50 people.

The Sri Lankan government had already pointed the figure at a little-known local Islamic extremist group called National Thowheeth Jama'ath (NTJ), but said it was investigating whether they had international support.

"Those that carried out the attack that targeted members of the US-led coalition and Christians in Sri Lanka the day before yesterday are Islamic State group fighters," a statement released by the group's propaganda agency Amaq said.

It presented no immediate evidence for the claim, or further details on the attackers.

But police sources in Sri Lanka told AFP that the attackers who targeted two of the hotels hit Sunday were Muslim brothers, sons of a wealthy Colombo spice trader.

Their names were not immediately revealed, but they were said to be in their twenties.

Guests were queuing for breakfast at the Shangri-La and Cinnamon Spice hotels when the two men detonated their bombs.

A fourth attack against a hotel on Sunday failed, sources also told AFP, though it was not immediately clear if the bomber's explosives had failed or he had chosen not to detonate them.

He later blew himself up when police tracked him to a lodging in the capital.

Police have detained at least 40 people as they investigate the worst act of violence in Sri Lanka since a civil war ended a decade ago.