(CNN) -- At least 359 people are now known to have died in a coordinated attack on churches and hotels on Easter Sunday in Sri Lanka, in what officials have called a "brand-new type of terrorism."
Police have arrested at least 40 people in connection with the suicide bombs, which injured at least 500 people, in the worst violence the South Asian island has seen since its bloody civil war ended 10 years ago.
Authorities were facing accusations that they had failed to act on a warning received ten days before the atrocity that an Islamist group was preparing an attack.
There were fears of more devices: A ninth improvised explosive device (IED) was defused near the capital's Bandaranaike International Airport on Sunday evening, according to an Air Force spokesman.
Most of the dead and injured were Sri Lankan. Of the foreign nationals who died, five were British citizens, two of whom held dual US-UK nationality; as well as three Indians, two Australians, two Chinese cousins, one person from the Netherlands, two Turkish citizens and one Portuguese national. The blasts appears to have targeted tourism hotspots, as well as churches, in an effort to gain maximum global attention.
No group has claimed responsibility, but Sri Lankan Defense Minister Ruwan Wijewardene said the "terrorist incident" was carried out by followers of "religious extremism."
On Sunday evening, a leaked memo revealed that police were warned of a potential attack by an Islamist group known as the Nations Thawahid Jaman (NTJ), ten days before the Easter Sunday bombings. It is unclear whether the details contained in the warning matched the atrocity that eventually took place.
Sri Lanka's Prime Minister, Ranil Wickremesinghe, said the intelligence was not shared with him or other ministers. Sajith Premadasa, minister of housing construction and cultural affairs, said officers were guilty of "negligence and incompetence."
There were doubts that the NTJ, a little-known group which has previously defaced Buddhist statues, would have had the capacity to carry out such a sophisticated and coordinated attack alone. Transnational Islamists are known to operate in places like Pakistan, Malaysia and the Philippines.
But Dhruva Jaishankar, a fellow in Foreign Policy Studies at Brookings India, said that little is known about Islamic radicalism in Sri Lanka and that it was "premature" to speculate on which organizations might have been involved.
A social media blackout was enforced in the aftermath of the attacks as authorities attempted to contain the violence and establish who carried out the attacks. A curfew was imposed from 8 p.m. to 4 a.m. local time.
How it unfolded
The first wave of attacks struck during packed Easter Sunday services between 8.45 a.m. and 9.30 a.m. local time. At St. Sebastian's Church in Negombo, north of the capital Colombo, more than 1,000 people had gathered for the holiest day in the Christian calendar. A blast tore through the church, killing 102 people, according to Father Edmond Tillekeratne, social communications director for the Archdiocese of Colombo.
As the Easter services got underway at churches in the cities of Colombo, Negombo and Batticaloa, the bombers detonated their devices. The bombs blew out the tiled roofs of churches, killing worshipers. Images showed bloodied pews, broken glass and plumes of smoke.
"You can see pieces of flesh thrown all over the walls and on the sanctuary and even outside of the church," Tillekeratne said.
More blasts ripped through three luxury hotels in Colombo: The Shangri-La, Cinnamon Grand and Kingsbury, all popular with foreign tourists and the country's business community. At the Shangri-La, the bomb was detonated just after 9 a.m local time at the Table One cafe as holidaymakers and guests were eating breakfast.
Later in the day, a blast rocked a hotel in front of the Dehiwala Zoo in Dehiwala-Mount Lavinia. The final blast struck a private house in Mahawila Gardens, in Dematagoda, during a raid in connection with the earlier attacks, officials said. Three police officers were killed.
Christianity is a minority religion in Sri Lanka, accounting for less than 10% of the total population of 21.4 million. According to census data, 70.2% of Sri Lankans identify as Buddhist, 12% Hindu, 9.7% Muslim, and 7.4% Christian. It is estimated that 82% of Sri Lankan Christians are Roman Catholic.
In recent years, Sri Lanka has boomed as a holiday destination, welcoming 2.2 million visitors in 2017 compared to just over one million in 2012, providing tourists with an affordable alternative to tropical destinations such as the Maldives.
On Monday morning, however, the city's beachfront hotel district, where several of the bombs struck, was heavily guarded by soldiers carrying AK47s and bomb-sniffing dogs were at closed hotel gates where guests were being checked in.
Rise of ISIS in Asia
Premadasa, the Sri Lankan minister, called Sunday's attacks a "brand-new type of terrorism" that had rocked the nation. "We have not had any separatist movements in the past 10 years and this came as a shock to all of us," he said.
The civil war between the separatist Tamil Tigers and the Sri Lankan government ended in 2009, after claiming between 70,000 and 80,000 lives. Handling that conflict, Premadasa said, had prepared the government to deal with terrorism.
"During the 30-year terrorist war there were indiscriminate attacks on all institutions, they (the Tamil Tigers) did not spare any in their path towards a separatist state, but we were victorious in defeating terrorism," he added.
The targets of the attacks -- churches and hotels catering to foreigners -- have figured in previous bombings in Asia and beyond in recent years. In January 2019, ISIS claimed responsibility for an attack that killed at least 20 in a church in the Philippines. The attack also took place on a Sunday, when worshipers were gathered for mass.
In May 2018, ISIS claimed responsibility attacks at three churches in Indonesia, which killed at least 12 people and injured dozens more. On Palm Sunday in 2017, ISIS killed at least 49 people gathered for Mass at two churches in Egypt.
After the collapse of the ISIS caliphate in Iraq and Syria, as many as 5,600 foreign fighters have returned to their home countries since October 2017.
Jaishankar, the analyst, said Sri Lanka may have become complacent about terrorism since the end of the civil war. "This may end up being a wake-up call for that," he said.