Islamic extremists carried out Sunday's coordinated attacks in retaliation for a March attack on two mosques in New Zealand, said Ruwan Wijewardana, the Sri Lankan State Defense Minister.

Addressing parliament today, Wijewardana said that initial investigations showed “the chain of bombings” was carried out by “a radical Islam group” which he named as the National Tawheed Jamath (NTJ).

No group has yet claimed responsibility.

Sri Lanka Police told CNN the death toll has now risen to 321 in the Easter Sunday bombing attacks.

Last month's mosque attack in Christchurch, New Zealand, saw at least 50 people murdered in a shooting rampage by a white supremacist. The rampage began at lunchtime on a Friday, when mosques were full of worshippers.