Sri Lanka's junior minister for defense, Ruwan Wijewardene, told parliament on Tuesday that an initial investigation had revealed the 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.
Security experts and analysts, however, have questioned whether the coordinated bomb attacks could have been planned in such a short period.
"We haven't received anything officially nor have we received any intelligence reports that corroborate what has been said in Sri Lanka," Ardern told reporters at a press conference in Auckland.
"Sri Lanka will be in the very early stages of its investigations. So we are simply stepping back and allowing them to undertake those, but we have nothing at this stage to corroborate what is being said," she added, Reuters reported.
Daesh (also known as ISIL or ISIS) 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 daesh.
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 Muslims at mosques in the NewZealand city of Christchurch during Friday prayers in March.
A lone gunman carried out those attacks, while livestreaming the massacre on Facebook.