Sri Lanka has vowed to “root out” extremism within its communities as Isis claimed responsibility for the Easter Sunday attacks that killed more than 320 people and left over 500 injured.

In a statement released on Tuesday by its Amaq propaganda agency, Isis said the attack was carried out by “fighters of the Islamic State”, and planned to target “nationals of the countries of the [anti-Isis, US-led] coalition” as well as “Christians in Sri Lanka”.

The coordinated attacks carried out by at least seven suicide bombers targeted international hotels and prominent Catholic churches in the capital Colombo, the western coastal town of Negombo and the former war-torn city of Batticalo in the east.

The group released images of eight men in black carrying knives, their faces covered, posing in front of an Isis flag, as well as a video in which they pledged allegiance to the Isis leader Abu Bakr al-Baghdadi.

A second, longer Isis statement released later referred to Easter as an “infidel holiday”, and to the carnage on Sunday as a “blessed invasion”. Sri Lankan authorities are investigating whether the cell which carried out the attack, previously identified as a local outfit named National Thowheed Jamath, was aided by returning fighters from Iraq and Syria.

Sri Lanka: Scene of the bomb attacks and aftermath Show all 38 1 /38 Sri Lanka: Scene of the bomb attacks and aftermath Sri Lanka: Scene of the bomb attacks and aftermath Sri Lankan Special Task Force officers raid a house following an explosion in capital Colombo AFP/Getty Sri Lanka: Scene of the bomb attacks and aftermath A blood-spattered statue of Jesus Christ while crime scene officials inspect the site of a bomb blast, as the sun shines through the blown-out roof, inside St Sebastian's Church in Negombo Reuters Sri Lanka: Scene of the bomb attacks and aftermath A police officer inspects the damage after a bombing at the Shangri-La Hotel in Sri Lankan capital Colombo AP Sri Lanka: Scene of the bomb attacks and aftermath Sri Lankan soldiers look on inside the St Sebastian's Church at Katuwapitiya in Negombo following a bomb blast during the Easter service AFP/Getty Sri Lanka: Scene of the bomb attacks and aftermath A woman cries next to a coffin of a bomb blast victim. A series of eight devastating bomb blasts ripped through high-end hotels and churches holding Easter services in Sri Lanka on April 21, killing more than 300 people AFP/Getty Sri Lanka: Scene of the bomb attacks and aftermath People who live near the church that was attacked the day before, leave their houses as the military try to defuse a suspected van before it exploded in Colombo Reuters Sri Lanka: Scene of the bomb attacks and aftermath Shoes and belongings of victims are collected as evidence at St Sebastian's Church AFP/Getty Sri Lanka: Scene of the bomb attacks and aftermath Sri Lankan police were forded to clear an area while Special Task Force Bomb Squad officers inspected the site of an exploded van near a church the day after it was attacked Reuters Sri Lanka: Scene of the bomb attacks and aftermath The Kingsbury Hotel in Colombo, Sri Lanka following a bombing AFP/Getty Sri Lanka: Scene of the bomb attacks and aftermath Queues at the National Blood Bank in Colombo, Sri Lanka after a request for blood to aid in recovery efforts Mr Lavasquabble/Twitter Sri Lanka: Scene of the bomb attacks and aftermath Medical response team work to remove dead bodies from the scene of bombings in Sri Lankan capital Colombo AFP/Getty Sri Lanka: Scene of the bomb attacks and aftermath Sri Lankan security personnel inspect the debris of a car after it exploded when police tried to defuse a bomb AFP/Getty Sri Lanka: Scene of the bomb attacks and aftermath Security personnel work at the scene of a bombing at a church in Batticaloa in Sri Lanka AFP/Getty Sri Lanka: Scene of the bomb attacks and aftermath A woman is helped near St Anthony's Shrine after a blast in Colombo, Sri Lanka, on Sunday 21 April 2019. At least 130 people were killed and more than 500 hospitalised after near-simultaneous explosions hit three hotels and three churches on Easter Sunday. AP Sri Lanka: Scene of the bomb attacks and aftermath Sri Lankan police officers clear the road as an ambulance drives through carrying injured of church blasts in Colombo, Sri Lanka, on Sunday 21 April 2019 AP Sri Lanka: Scene of the bomb attacks and aftermath A Sri Lankan soldier stands guard near a car explosion AFP/Getty Sri Lanka: Scene of the bomb attacks and aftermath A woman prays at St. Sebastian's Church in Negombo AFP/Getty Sri Lanka: Scene of the bomb attacks and aftermath Priests stand inside St Anthony's Shrine, Kochchikade church on the outskirts of Colombo after a bombing Reuters Sri Lanka: Scene of the bomb attacks and aftermath A Sri Lankan woman living near St. Anthony's shrine runs for safety with her infant after police found explosive devices in a parked vehicle in Colombo AP Sri Lanka: Scene of the bomb attacks and aftermath People react during a mass for victims, two days after a string of suicide bomb attacks on churches and luxury hotels Reuters Sri Lanka: Scene of the bomb attacks and aftermath Security personal react as a device was detonated in a controled explosion in a van near the St Anthony's Church EPA Sri Lanka: Scene of the bomb attacks and aftermath Security forces inspect the scene of a bombing at the Shangri-La Hotel in Sri Lankan capital Colombo Getty Sri Lanka: Scene of the bomb attacks and aftermath The Kingsbury hotel in Colombo, Sri Lanka after a bombing attack Getty Sri Lanka: Scene of the bomb attacks and aftermath The damaged interior of a church in Negombo, Sri Lanka following a bombing attack Reuters Sri Lanka: Scene of the bomb attacks and aftermath Police and security personnel stand guard outside the Shangri-La Hotel in Sri Lankan capital Colombo following a bombing attack EPA Sri Lanka: Scene of the bomb attacks and aftermath Debris is seen at St Anthony's Church in this still image from video footage after explosions hit churches and hotels in Colombo, Sri Lanka, on 21 April 2019 Derana TV/via Reuters Sri Lanka: Scene of the bomb attacks and aftermath Damage inside a church following a bombing attack AP Sri Lanka: Scene of the bomb attacks and aftermath A Sri Lankan Special Task Force officer scales a house during a raid following an explosion in capital Colombo AFP/Getty Sri Lanka: Scene of the bomb attacks and aftermath A general interior view showing damage after an explosion hit St Anthony's Church in Kochchikade, Colombo, Sri Lanka, on Sunday 21 April 2019 EPA Sri Lanka: Scene of the bomb attacks and aftermath Priests walk into St Anthony's Shrine Kochchikade church after an explosion in Colombo, Sri Lanka, on 21 April 2019 Reuters Sri Lanka: Scene of the bomb attacks and aftermath A Sri Lankan police officer stands outside St Anthony's Shrine in Colombo, Sri Lanka, after a blast on Sunday 21 April 2019 AP Sri Lanka: Scene of the bomb attacks and aftermath A shoe of a victim is seen in front of the St Anthony's Shrine, Kochchikade Church Reuters Sri Lanka: Scene of the bomb attacks and aftermath Local and security officials gather at the scene at St Anthony's Church in Kochchikade, Colombo, Sri Lanka EPA Sri Lanka: Scene of the bomb attacks and aftermath An ambulance is seen outside the church premises with gathered security personnel following a blast at St Anthony's Shrine in Kochchikade, Colombo, on Sunday 21 April 2019 AFP/Getty Sri Lanka: Scene of the bomb attacks and aftermath Armed policemen patrol the area after an explosion hit at St Anthony's Church in Kochchikade in Colombo, Sri Lanka, 21 April 2019 EPA Sri Lanka: Scene of the bomb attacks and aftermath Sri Lankan Army soldiers secure the area around St. Anthony's Shrine after a blast in Colombo, Sri Lanka, Sunday 21 April 2019 AP Sri Lanka: Scene of the bomb attacks and aftermath Sri Lankan security personnel keep watch outside the church premises following a blast at the St Anthony's Shrine in Kochchikade, Colombo, on Sunday 21 April 2019 AFP/Getty Sri Lanka: Scene of the bomb attacks and aftermath Police officers inspect the scene after an explosion hit at St Anthony's Church in Kochchikade in Colombo, Sri Lanka, 21 April 2019 EPA

Not long before the group’s claim to the attacks, Sri Lankan junior defence minister Ruwan Wijewardene issued a statement saying intelligence showed Sunday’s bombings were in retaliation for last month’s Christchurch shootings.

In New Zealand, a lone gunman opened fire on two mosques, killing 50 people and leaving dozens injured.

“Preliminary investigations have revealed that what happened in Sri Lanka was in retaliation for the attack against Muslims in Christchurch,” Mr Wijewardene told the Sri Lankan parliament, without providing evidence of his source.

In an interview with The Independent as news of Isis’s claim emerged, the Sri Lankan minister of Muslim affairs Mohammed Hashim Abdul Haleem said that the possibility of the group’s involvement had been discussed at cabinet level in the past two days.

Sri Lanka minister claims church bombings were 'retaliation for Christchurch mosque shootings'

He said the prime minister warned a parliamentary group that met on Monday evening that “this is another war that is starting”, referring to the island’s three decade war with the Tamil Tigers. The ethnic war that ended in 2009 claimed around 100,000 lives, with over 160 suicide attacks carried out by Tamil militants.

Mr Haleem said: “If this Isis is camouflaging among our community, we have to come together as Muslims and root them out.

“It is a war against fanaticism, which must be waged by the government and by the people of Sri Lanka.”

Sri Lanka would also “look to international partners”, he said, adding that security advisers from the US and Interpol were already working with the government in Colombo. “So many countries have come forward to offer their support,” he added.

It was “shocking”, Mr Haleem said, that Sri Lanka appeared to have become a new front in the fight against Isis, “but the world is fighting this war with us”.

Two days after the bombings, the Sri Lankan government announced a day of mourning on Tuesday, and requested a three minute island-wide silence at 08:30 local time [03:00 GMT] in respect for those killed. As white flags fluttered at offices and residences in Colombo, the capital came to a standstill and the streets were deserted long before the government imposed a 9pm curfew, the third in three nights.

President Maithripala Sirisena has declared a “state of emergency” that gives police powers to detain suspects without a warrant. The police spokesman said on Tuesday that 40 people have been arrested so far in connection to the attacks.

And as Prime Minister Ranil Wickremesinghe told reporters there could be more bombs and militants “out there”, all police stations in the capital were placed on high alert regarding reports of a van and a lorry carrying explosives.

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A senior police source told The Independent that the threat was “far from over”. Eyewitnesses said that police were investigating a suspicious vehicle near the Kingsbury Hotel, which was one of the locations where a suicide bomber blew himself upon Sunday.

Minutes later, civilians at the capital’s World Trade Centre, the government-run Bank of Ceylon and the Ceylon Chamber of Commerce, were evacuated from their premises.

As bodies of the victims were being buried around the island on Tuesday, officials and priests of the attacked churches said the death toll following the attacks could end up being much higher than the current official figures.

“The exact number of the dead is hard to determine at the moment because the churches were crowded and many of the bodies have been blasted into pieces,” said a government official.

Father B A Shiran of St Nicholas’s church in Negombo told The Independent that while the official death toll for the attack at St Sebastian’s church in the town was 110, he believed the number of worshippers who died there would emerge to be more than 200.

A health official at the Colombo National hospital, where most of the injured were rushed following Sunday’s attacks in the capital, confirmed that 267 patients were admitted in the hours following the blasts and 53 had died at hospital so far.

“There were many severe burn and head injuries. More than 15 brain surgeries were carried out yesterday alone and we expect many more casualties,” said the official, who did not want to be named.

With the Muslims’ Friday congregational prayers approaching, the Muslim affairs minister told The Independent that he fears there will be a major backlash against the community.

“We have requested the armed forces to provide security around the mosques during the Friday prayers,” said the minister, who called the attacks “shocking and shameful to face as a community”.

Mr Haleem also said that the Security Council refused to provide security to representatives of the Muslim community who were keen on participating in the funeral services of the victims.

“The defence advised us not to visit these places at this hour as emotions are high,” said the minister.

The minister said that Sunday’s attacks and emerging evidence against “certain minority elements” in the Muslim community shows there is much work to be done to “weed out terrorism”.

Video shows moment van explodes in Colombo, Sri Lanka

“Terrorism has no religion,” said the minister, asking the Muslim community to come forward to help rebuild.

“Each and every one of us should lend our monetary and other resources to help rebuild the churches that have been destroyed,” he said. “I urge the Muslim community to stand together with our Christian brothers at this time of need and help out in every way possible.”

Amid criticism of President Maithripala Sirisena’s government over its failure to act on intelligence shared weeks before the multiple blasts, Mr Haleem said it was “time to end the blame game” and look ahead at ways to rebuild the nation.

Addressing the nation on national television on Tuesday night, President Sirisena said he would be sacking the heads of the country’s defence forces within a day for their neglect.

“I will completely restructure the police and security forces in the coming weeks. I expect to change the heads of defence establishments within next 24 hours,” said the president.