ISIS has claimed responsibility for the deadly Easter bombings in Sri Lanka that killed at least 321 people.

In a statement Issued through ISIS’official channel, the terrorist group said two domestic Islamist groups in Sri Lanka carried out the coordinated attacks on three churches and four hotels on Easter Sunday.

The Sri Lanka government has hinted that the bombings might have been in retaliation for shootings by a white supremacist at two New Zealand mosques that left 50 worshippers dead. The US’ FBI has joined forces with Sri Lanka’s SIS intelligence service to help with the investigation, said according to officials familiar with the matter.

The Islamic State has identified the seven suicide bombers by their noms-de-guerre and said each site was targeted to inflict the maximum number of casualties on civilians during what it called “an infidel holiday.”

Sri Lankan Prime Minister Ranil Wickremesinghe said the terrorists were backed by foreign elements, and some investigators believe the attackers travelled to Syria prior to the attack. The did say, however, that there are no links to Islamic militants fighting in the Syrian Civil War have been established.