COLOMBO, Sri Lanka — Sri Lanka's defense minister said Tuesday that the coordinated Easter Sunday attacks that killed at least 321 people were in retaliation for the recent Christchurch mosque massacre in New Zealand.

"Extremist group named National Thowheed Jamaath carried out Sunday's terror attacks in response to terror attacks in Christchurch," Defense Minister Ruwan Wijewardene said.

The shootings in March in New Zealand killed 50 people and led the country to take swift action to approve new gun control laws.

New Zealand officials classified the alleged gunman in the Christchurch shooting as a "right-wing extremist terrorist" who appeared to post a manifesto detailing his white-supremacist worldview and who had donated to a far-right Austrian group.

Wijewardene offered little evidence to support the link between the two attacks, not revealing his source.

New Zealand officials said they are not able to confirm the connection.

"New Zealand has not yet seen any intelligence upon which such an assessment might be based," the office of Prime Minister Jacinda Ardern said in a statement.

Sri Lanka is primarily Buddhist, with significant Muslim, Christian and Hindu minorities. While anti-Muslim bigotry has risen in the country recently, there isn't a history of violence and tension between the country's Muslim and Christian communities.

Wijewardene also said the "weakness" of Sri Lanka's security apparatus, which had received warnings of an impending attack on the nation's churches, is to blame for failing to prevent the bombings, according to The Associated Press.

"We never expected it to be so big," Hemasiri Fernando, the chief of staff to Sri Lanka's president, told NBC News on Monday. "We never thought it would happen so soon."

Two days after the attack, the Islamic State militant group claimed responsibility but produced no evidence to support the claim.

The coordinated attacks, which set off a wave of concurrent explosions, hit three churches and three luxury hotels. Among the dead was an 11-year-old student from Washington, D.C., who was having breakfast with his family.

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Two siblings, Amelie Linsey, 15, and Daniel Linsey, 19, who were dual U.S.-U.K. citizens, were also killed while eating breakfast at the Shangri-La Hotel on the last day of a family vacation.

At least 375 people were injured in the attacks.

After the bombing, Sri Lankan authorities blocked social media, saying it would halt the spread of false information and hopefully reduce tensions throughout the country.

Laxman reported from Colombo, Kesslen from New York.