Sri Lanka's junior minister for defense, Ruwan Wijewardene, told his country's parliament on Tuesday that an initial investigation had revealed the coordinated bombings on churches and hotels, which killed 321 people, had been carried out in revenge for deadly shootings in two New Zealand mosques on March 15.
Ardern's office said the prime minister had seen reports of the minister's statement.
"We understand the Sri Lankan investigation into the attack is in its early stages. New Zealand has not yet seen any intelligence upon which such an assessment might be based," a spokeswoman for Ardern said in an emailed statement.
Islamic State (IS) claimed responsibility for the Sri Lanka attacks on Tuesday and named what it said were seven attackers who carried them out. It gave no further evidence to support its claim of responsibility.
Prime Minister Ranil Wickremesinghe told a news conference investigators were making progress in identifying the perpetrators and believed there could be some links to IS.
Sri Lanka's junior defense minister had earlier told Parliament that two Sri Lankan Islamist groups - the National Thawheed Jama'ut and Jammiyathul Millathu Ibrahim - were responsible for the blasts early on Sunday during Easter services and as high-end hotels served breakfast.
He did not elaborate on why authorities believed there was a link to the killing of 50 people at mosques in the New Zealand city of Christchurch during Friday prayers in March. A lone gunman carried out those attacks. A suspected white supremacist has been charged with murder in connection to the shootings.
"New Zealanders oppose terrorism and extreme violence in all its forms. In the wake of the Christchurch mosque attacks, it was the condemnation of the perpetrators of violence and a message of peace that unified us all," Ardern's spokespeson added. (Reporting by Charlotte Greenfield; Editing by Cynthia Osterman)