At least 290 people died in Sri Lanka on Easter Sunday in a wave of bombings that was carried out with the support of an international network, officials said.

The Sri Lankan government has blamed a little-known local jihadist group, National Thowheed Jamath, although no-one has yet admitted carrying out the bombings.

Another 500 people were injured in the suicide attacks on churches and hotels.

Twenty four people have been arrested in a series of raids and President Maithripala Sirisena’s office declared a state of national emergency.

Sri Lanka Attacks: At Least 137 Killed in Churches and Hotels Explosions on Easter Sunday

The state of emergency declaration, which comes into effect from midnight on April 22, will give police and military extensive powers to detain and interrogate suspects without court orders.

On April 22, another blast rocked a street near a church in the capital, Colombo. Police were attempting to defuse explosives in a vehicle used by the attackers when it blew up. It is not yet known if anyone was hurt.

Sri Lankan authorities were warned about a bomb threat from National Thowheed Jamath a full two weeks before the attacks, cabinet spokesman Rajitha Senaratne said at a press conference.

He said that the warnings were not passed on to PM Ranil Wickremesinghe or his cabinet. The prime minister acknowledged that security services had been “aware of information” but had not acted on the information.

Rajitha Senaratne said that authorities believed the bombers had international support.

“We do not believe these attacks were carried out by a group of people who were confined to this country,” he said.

“There was an international network without which these attacks could not have succeeded,” he added.

A later statement said President Maithripala Sirisena would ask for foreign help to track down the international links to the attackers.

“The intelligence reports that foreign terrorist organizations are behind the local terrorists. Therefore, the president is to seek the assistance of the foreign countries,” his office said.

A curfew is to be imposed from 20:00 April 22 until 04:00 on April 23, the government said. A national day of mourning has been scheduled for April 23.

Sri Lanka’s National Security Council said a “conditional state of emergency” from midnight would target “terrorism” and would not limit freedom of expression.

In another development, the US State Department issued revised travel advice urging greater caution, adding: “Terrorist groups continue plotting possible attacks in Sri Lanka.”

The first reports of explosions came at about 08:45 local time on April 21with six blasts reported within a small space of time.

Three churches in Negombo, Batticaloa and Colombo’s Kochchikade district were targeted during Easter services. Blasts also rocked the Shangri-La, Kingsbury and Cinnamon Grand hotels in the country’s capital, Colombo.

Police did not release a breakdown of how many people were killed and wounded at each location.

All the attacks were carried out by suicide bombers, officials said.

Police then carried out raids on two addresses and there were explosions at both. One was in Dehiwala, southern Colombo, and the other was near the Colombo district of Dematagoda in which three officers were killed.

An improvised explosive device – a 6ft-long plastic pipe packed with explosives – was also found and defused near the airport in Colombo.

Police also recovered 87 low-explosive detonators from the Bastian Mawatha private bus station in Pettah.