New Zealand security expert Paul Buchanan says it's unlikely that coordinated bomb attacks in Sri Lanka were a response to the Christchurch mosque shootings.

Buchanan's comments follow claims on social media from Islamic State supporters who boasted that the attacks were revenge for the Christchurch massacre last month.

Buchanan, director of 36th Parallel Assessments, said given the co-ordinated nature of the Sri Lankan bombings and intel warnings which were ignored, it would seem a month was too little time to prepare for such an attack.

Security expert Paul Buchanan. Photo / File
Security expert Paul Buchanan. Photo / File

SITE Intelligence Group director Rita Katz says IS supporters had boasted on social media that Colombo was revenge for Christchurch.

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Katz said IS media channels were "posting rampantly" about the explosions and praying "may Allah accept" the attackers, indicating the group may be planning to claim responsibility.

"While such a claim may frame the op as revenge for New Zealand, this was likely planned long before," she said.

Buchanan said the attack appears to be an attempt to sow sectarian hatred in Sri Lanka, also adding they appear to have been planned prior to the March 15 events.

Sri Lankan military officers stand guard in front of St Anthony's Church in Kochchikade, Colombo. Photo / Getty Images
Sri Lankan military officers stand guard in front of St Anthony's Church in Kochchikade, Colombo. Photo / Getty Images

"Christchurch seems to be a convenient justification for something that was being planned before March 15 and has more to do with ethnic-religious conflict in Sri Lanka," he said.

"It does show the dangers of tit for tat responses to terrorist attacks of any stripe, as it feeds into the clash of civilisations narrative."

No group has officially claimed responsibility for the blasts, which ripped through three churches, four luxury hotels and a unit block in Colombo.

This image made from video provided by Hiru TV shows damage inside a church after a blast in Colombo. Photo / AP
This image made from video provided by Hiru TV shows damage inside a church after a blast in Colombo. Photo / AP

Scores more died in attacks in Negombo and Kochchikade, north of the capital, and Batticaloa in the island nation's east.

The explosions are the deadliest violence in the country since its civil war ended a decade ago, the Washington Post reported.

The decade that followed has been largely peaceful - few have been killed in any terrorism-related attacks in Sri Lanka.

Sri Lankan Army soldiers secure the area around a church after a blast in Colombo, Sri Lanka. Photo / AP
Sri Lankan Army soldiers secure the area around a church after a blast in Colombo, Sri Lanka. Photo / AP

However, Buddhist nationalism has become its own form of violence, albeit far less deadly than civil war.

The attacks appear to be another turn toward religious-based violence.

Additional reporting from News.com.au and Washington Post