Islamic State supporters are celebrating the Sri Lanka suicide bombings which killed 290 people on Easter Sunday and left around another 500 injured.

Fanatics were also said to be praising the terror attacks as revenge for the Christchurch mosques shooting.

No group has officially claimed responsibility for the blasts at five-star hotels and churches but Sri Lankan police say a previously unknown Muslim extremist group were the subject of an intelligence warning ten days before.

SITE Intelligence Group director Rita Katz said IS supporters have applauded the attacks on social media, 'celebrating casualties'

ISIS militants marching in Raqqa, Syria, in 2014. This year the fundamentalists were driven from the last land they occupied but security experts have warned of 'pop up' terror cells

A view of St. Sebastian's Church, which was damaged in the blast in Negombo, north of Colombo, on Sunday morning

Early evidence points towards Islamist group National Thowheed Jamaath (NTJ), according to intelligence chiefs, who warn that more attacks are expected.

Rita Katz, director of respected terror monitoring SITE Intelligence Group, said IS supporters have applauded the attacks on social media, 'celebrating casualties'.

Ms Katz said IS media channels were ‘posting rampantly’ about the blasts and praying ‘may Allah accept’ the suicide bombers.

She claimed that the online praise indicated the group may be preparing to take responsibility for the attacks.

Sri Lankan security officials said they were investigating. Police immediately sealed off the areas (pictured: St Anthony's Shrine)

A map showing where the eight blasts went off, six of them in very quick succession on Easter Sunday morning

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

Australian born Brenton Tarrant is facing 50 counts of murder and 39 counts of attempted murder after opening fire on two mosques in Christchurch on March 15.

Fighters from Sri Lanka have been mentioned in ISIS ranks and the country would be ‘easily accessible’ for fanatics, Ms Katz said.

Several Sri Lankan Muslims from ‘well-educated and elite’ families were known to have joined the terror group in Syria, according to Reuters.

The attacks follow just weeks after ISIS launched a global military initiative branded the ‘Revenge Invasion’ as payback for the loss of their territory in Syria.

Police have so far arrested 13 people over the Sri Lanka attacks, describing those in custody only as ‘religious extremists’.

Ten days ago, according to documents seen by the AFP new agency, Sri Lanka's police chief Pujuth Jayasundara issued an intelligence alert to top officers warning Islamist suicide bombers planned to hit 'prominent churches'.

A crime scene official inspects the site of a bomb blast inside a church in Negombo, Sri Lanka, which lost half its roof tiles with the force of the blast

Security forces inspect the St. Anthony's Shrine after an explosion hit St Anthony's Church in Kochchikade in Colombo

Wreckage: Sri Lankan security personnel inspect the damage at St Anthony's Shrine following the Easter Sunday bombing

'A foreign intelligence agency has reported that the NTJ (National Thowheeth Jama'ath) is planning to carry out suicide attacks targeting prominent churches as well as the Indian high commission in Colombo,' the alert said.

The NTJ is a small radical Muslim group in Sri Lanka which has no history of mass fatal attacks, but came to prominence last year linked to the vandalism and desecration of Buddhist statues.

Prime minister Ranil Wickremesinghe admitted that information about the attacks had been received in advance but denied having direct knowledge himself.

'We must look into why adequate precautions were not taken. Neither I nor the ministers were kept informed,' he said following intense anger in the community.

Manisha Gunasekera, the Sri Lankan High Commissioner to the UK, has said eight British nationals were killed in the attacks.

Three of the near-simultaneous blasts targeted worshippers attending Easter services on the holiest day in the Christian calendar.

Families on holiday were massacred by three further explosions at luxury hotels in Colombo as they sat down to enjoy breakfast at around 8.30am.

Sri Lanka's Foreign Ministry said the bodies of at least 27 foreigners were recovered. Foreign Secretary Jeremy Hunt condemned the the 'horrifying attacks' which he said had killed 'several British nationals'.

Further fatalities are said to include three Indians, two Turks, one Portuguese citizen and an unknown number of Dutch and Chinese nationals.

Sri Lanka's defence ministry has now ordered curfew with immediate effect 'until further notice' while access to social media messaging services has been shut down.

In Colombo, St Anthony's Shrine, a Roman Catholic church, the Cinnamon Grand; Shangri-La; and Kingsbury hotels were targeted in the first wave of explosions.

Sri Lankan soldiers secure the area around St. Anthony's Shrine after a blast in Colombo on Easter Sunday

At the Shangri-La, security camera footage showed two men detonating devices in the Table One restaurant and a hotel corridor.

Other blasts hit St Sebastian's Church in Negombo, a majority Catholic town north of Colombo, and at Zion Church in the eastern town of Batticaloa.

Later in the afternoon, two died in a strike at a hotel near a zoo in the south of Colombo, before a suspected suicide bomber killed police officers in the suburb of Orugodawatta in the north of the capital, as police moved in on the suspected terrorist safe house. In all 13 suspects were arrested.

Sri Lanka defence secretary Harsha de Silva said: 'Horrible scenes, I saw many body parts strewn all over.'

The terror attack was Sri Lanka's deadliest violence since a devastating civil war in the South Asian island nation ended a decade ago.

Prime Minister Theresa May joined leaders across the world in condemning the atrocities while President Donald Trump vowed to 'stand ready to help'.

Millions of tourists visit Sri Lanka every year but political crisis and religious tension have placed the industry under threat in recent months.