New Zealand at the centre of global crisis if Sri Lanka bombings retaliation for Christchurch shootings - expert

While admitting information is scant, one terrorism expert says the Sri Lanka Easter Sunday bombings did appear to be retaliation for the Christchurch shootings, putting New Zealand at the centre of a "global crisis".

On Tuesday, Sri Lankan Defence Minister Ruwan Wijewardene said preliminary investigations into the series of explosions across Sri Lanka which killed 321 people found they were retaliatory attacks to the March 15 Christchurch shootings.

The Guardian reported an intelligence memo circulated to some in the Sri Lankan government in the weeks before the attack said one suspected perpetrator of the attacks had started to update his social media accounts "with extremist content" in the aftermath of the Christchurch shootings.

Waikato University Professor of Law Al Gillespie said while it was based only on conjecture, it looked like the attacks were a "reprisal", where Christian churches in Sri Lanka were bombed in retaliation to Muslims being shot in mosques in Christchurch.

"What you have here, fundamentally, is what looks like a reprisal, where one sanctuary has been attacked in exchange for another sanctuary, based on the basis of religion.

"It puts us at the centre of a global crisis because right now, the shooting starts at Christchurch, it goes to Sri Lanka, and normally what happens with reprisal, it goes tit for tat.

"This is exactly what the Christchurch murderer wanted, he wanted them to respond, and now the risk is that someone else will follow in the same suit, but against another Muslim community."

He said the Sri Lankan Defence Minister's comments would serve to take heat off the Sri Lanakan Government's own faults - primarily that some officials had seen intelligence memos warning of a potential attack prior to Sunday.

But the comments have caught some off guard, with Prime Minister Jacinda Ardern's office releasing a statement saying New Zealand officials had "not yet seen any intelligence upon which such an assessment might be based".

National Party leader Simon Bridges was also cautious about the comments, noting the lack of evidence yet provided to support the claim and the amount of preparation likely behind the Easter Sunday bombings was more than achievable in the period since March 15.

"I would be really cautious about what has been said by the Sri Lankan minister, and that's not because I know anything in particular, other than to say, look what we do know is this has been well prepared, so you would have to say it hasn't been a new thing potentially," he told The AM Show.

"So I would just be cautious in the absence of evidence."

International relations expert Robert Patman also told Newshub that the timelines didn't match up.

"If we are correct, that the Sri Lanka operation was planned a long time ago, it can't be accurately depicted as simple retaliation to the appalling atrocity in Christchurch.

"To immediately react, as the defence minister has done, by drawing an apparent linkage between what happened in Sri Lanka and what happened in Christchurch, seems to me a bit premature."

Gillespie admitted "a lot of things don't add up here", including the preparation time, but he said Christians hadn't previously been targets for local extremists.

"To do an attack like this would take a lot of preparation, getting the materials, planning it, surveillance, handling the suicide bombers, and that would take much longer normally than the period that you have here.

"The groups that are involved were primarily against Buddhist targets and vandalism before this event, something changed, something changed in the orientation towards the Christian targets and the hotels, and something changed in their military capability."

The local Islamist group, National Thawheed Jama'ut (NTJ), suspected of carrying out the attacks, may have been supported by Islamic State, which claimed responsibility for the bombings on Tuesday.

The AM Show's Channel 7 correspondent Hugh Whitfeld said investigators would look into their role in Sunday's tragedy.

"[This group has] been operating here in Sri Lanka for some time, and most people don't think that that group alone could have carried out these attacks because of the level of sophistication involved, so an outside body must have been helping them, like IS.

"More than 30 Sri Lankans have travelled to Syria to fight with IS in recent years. Some of them have returned home and part of the investigation will no doubt focus on whether they returned home with skills to help radicalise fellow Muslims here in Sri Lanka."