Junior defence minister Ruwan Wijewardene made the comment to politicians in Parliament on Tuesday, without providing evidence or explaining where the information came from.
“This attack was carried out in retaliation for the attack against Muslims in Christchurch,” he said, adding that two domestic Islamist groups were believed to be responsible.
“It was done by National Thawheed Jama’ut along with JMI,” he said, referring to another local group, Jammiyathul Millathu Ibrahim.
The Guardian’s south Asia correspondent, who attended the briefing, tweeted that one of the suspects had been updating his social media accounts “with extremist content” in the aftermath of the New Zealand shootings on March 15.
It comes after New Zealand security expert Paul Buchanan said it was unlikely the attacks were carried out in retaliation, telling the New Zealand Herald a month was too little time to prepare for such an attack.
Police have arrested 40 suspects in connection with the Easter attacks, which saw 321 people lose their lives. Eight Britons have been confirmed dead.
No group has claimed responsibility for the attacks, which officials said were carried out by at least seven suicide bombers on three churches and four hotels. About 500 people were also wounded.
Tuesday was declared a national day of mourning, with widespread mass funerals held.
Last month’s attacks in New Zealand saw 50 people killed in two mosques by a gunman who streamed his actions on social media.