A Sri Lanka government minister says the Easter Sunday bombings which killed more than 300 people were retaliation for the Christchurch mosque attacks.

State Minister of Defence Ruwan Wijewardene told Sri Lankan Parliament initial investigations showed the co-ordinated attacks were "carried out in retaliation for the attack against Muslims in Christchurch".

Wijewardene said two domestic Islamic organisations were responsible for the bombings, including National Thawheed Jama'ut (NTJ).

Meanwhile, Prime Minister Jacinda Ardern's office said they have "not yet seen any intelligence upon which such an assessment might be based", Stuff reported.

Sri Lankan intelligence has named the mastermind behind the Easter Sunday attacks as Moulvi Zahran Hashim, an extremist local cleric who incited his followers to violence with fiery sermons on his social media channels.

The revelation comes after senior government officials accused the NTJ, a little-known group promoting Islamist terrorist ideology, as the perpetrators of the horrific suicide bombings which have now killed 310 people, including eight British citizens.

India's CNN News 18 channel first reported the possible involvement of Hashim in the massacre, claiming Indian intelligence sources had indicated to the Sri Lankans that he was planning to attack the Indian High Commission in Colombo in early April.

Over the past two years, Hashim gained thousands of followers and attracted the attention of jihad experts for his incendiary preaching on a pro-Islamic State Sri Lankan Facebook account, known as "Al-Ghuraba" media, and on YouTube.

Robert Postings, a writer and researcher on Islamic State (Isis), said on his Twitter account he had first encountered Hashim in late 2017 when the "self-styled" preacher was disseminating pro-Isis propaganda on Facebook.

YouTube videos of the Islamist who is now the face of one of the worst terrorist atrocities since 9/11 shows him railing against all non-believers, including Christians, Hindus and Buddhists, and declaring only Muslims are fit to rule. The backdrop to his sermons included images of the burning Twin Towers in New York in 2001.

Three days after the Sri Lankan attack there have been no claims of responsibility by Isis, the NTJ, or any other group for the series of six devastating bombings across three hotels and three churches on Sunday.

There have also been conflicting reports about the fate of Hashim, with claims circulating that he was one of the suicide bombers who carried out the attack and counter-claims that he may be on the run in the neighbouring Maldives islands.

Although known primarily as a luxury honeymoon destination, the Maldives also supplied hundreds of radicalised fighters to Isis' failed attempts to set up an Islamic caliphate in the Middle East.

Hashim himself was known among the Muslim community as a divisive figure who was said to have dropped out of his seminary in India either because of ideological differences or over money worries. He is believed to have clashed with fellow clerics and encouraged his followers to attack rival mosques.

Hilmy Ahamed, the vice-president of the Muslim Council of Sri Lanka, told the Telegraph he had been trying to warn officials about Hashim's extremism for three years after it emerged that he was radicalising young pupils in his Koran classes.

"We were very concerned that this guy was preaching hate on social media and uploading a lot of videos," Ahamed said.

He said Hashim continued to shuttle between India and Sri Lanka, travelling by fishing boat to avoid detection.

Hashim's group began as an offshoot of the Sri Lanka Thawheed Jama'ut, which has repeatedly fractured due to internal disputes.

The group could not have carried out the attack without external help, added Ahamed.

One working theory among regional security experts is that returning fighters could have provided training and logistics to the marginal NTJ which, although a cheerleader of global jihad, had only been known previously for defacing Buddhist statues in Sri Lanka.

In January, police in Puttalam, about 160km north of Colombo, raided a coconut plantation, where they discovered 100kg of C4 explosives, 100 detonators, 75kg of ammonium nitrate and potassium chlorate and six 20-litre cans of nitric acid.

Reports at the time did not name the group involved but said the site may be linked to a newly emerging militant group that was tied to the vandalising of Buddhist statues. Suspects were arrested but later released on bail.

Three months later, Sri Lankan security agencies received a tip-off from Indian and United States intelligence agencies that the NTJ may be preparing to carry out terrorist acts against churches, but the crucial information was not passed to Sri Lanka's Prime Minister, Ranil Wickremesinghe.

Since the attacks, the Sri Lankan Government has apologised for failing to act on the intelligence brief.