The coordinated Easter Sunday bombings that ripped through Sri Lankan churches and luxury hotels, killing more than 290 people, were carried out by seven suicide bombers from a domestic terrorist group named National Thowfeek Jamaath, a government official said Monday.

All of the bombers were Sri Lankan citizens, but authorities suspect foreign links, Health Minister Rajitha Senaratne said at a news conference.

Government spokesman Rajitha Senaratne, who is also a cabinet minister, said Monday that the government was investigating whether the group had "international support."

Earlier, Ariyananda Welianga, a government forensic crime investigator, said an analysis of the attackers' body parts made clear that they were suicide bombers. He said most of the attacks were carried out by a single bomber, with two at Colombo's Shangri-La Hotel.

"We do not believe these attacks were carried out by a group of people who were confined to this country," Rajitha Senaratne said. "There was an international network without which these attacks could not have succeeded."

An analysis of the attackers' body parts made clear that they were suicide bombers, said Ariyananda Welianga, a forensic crime investigator. He said most attacks were by one bomber, with two at Colombo's Shangri-La Hotel.

The bombings, Sri Lanka's deadliest violence since a devastating civil war ended a decade ago on the island nation, killed at least 290 people with more than 500 wounded, police spokesman Ruwan Gunasekara said Monday.

Police have arrested at least 24 people in connection to the attacks, Gunasekara said.

Gunasekara said that the individuals arrested, all locals were being questioned by the Criminal Investigation Department.

Meanwhile, Sri Lankan police investigating the bombings are examining reports that intelligence agencies had warnings of possible attacks, officials said Monday.

International intelligence agencies warned of the attacks several times starting April 4, Health Minister Senaratne said. On April 9, the defense ministry wrote to the police chief with intelligence that included the group's name, he said. On April 11, police wrote to the heads of security of the judiciary and diplomatic security division, Senaratne said.

It was not immediately clear what action, if any, was taken in response. Authorities said little was known about the group except that its name had appeared in intelligence reports.

Two government ministers have alluded to intelligence failures. Telecommunications Minister Harin Fernando tweeted, "Some intelligence officers were aware of this incidence. Therefore there was a delay in action. Serious action needs to be taken as to why this warning was ignored." He said his father had heard of the possibility of an attack as well and had warned him not to enter popular churches.

And Mano Ganeshan, the minister for national integration, said his ministry's security officers had been warned by their division about the possibility that two suicide bombers would target politicians.

The police's Criminal Investigation Department, which is handling the investigation into the blasts, will look into those reports, Gunasekara said.

The explosions — mostly in or around Colombo, the capital — collapsed ceilings and blew out windows, killing worshippers and hotel guests in one scene after another of smoke, soot, blood, broken glass, screams and wailing alarms.

A morgue worker in the town of Negombo, outside Colombo, where St. Sebastian's Church was targeted, said many bodies were hard to identify because of the extent of the injuries. He spoke on condition of anonymity.

At the Shangri-La Hotel, a witness said "people were being dragged out" after the blast.

"There was blood everywhere," said Bhanuka Harischandra a 24-year-old from Colombo and founder of a tech marketing company. He was heading to the hotel for a meeting when it was bombed. "People didn't know what was going on. It was panic mode."

Most of those killed were Sri Lankans. But the three bombed hotels and one of the churches, St. Anthony's Shrine, are frequented by foreign tourists, and Sri Lanka's Foreign Ministry said the bodies of at least 27 foreigners from a variety of countries were recovered.

The U.S. said "several" Americans were among the dead, while Britain, India, China, Japan and Portugal said they, too, lost citizens.

The streets were largely deserted Monday morning, with most shops closed and a heavy deployment of soldiers and police. Stunned clergy and onlookers gathered at St. Anthony's Shrine, looking past the soldiers to the stricken church.

Sri Lankan authorities on Monday ordered a state of emergency to be introduced from midnight Monday following the deadly Easter attacks, the president's office said.

The special measures are being brought in "to allow the police and the three forces to ensure public security," the statement said, referring to the army, navy and air force.

Prime Minister Ranil Wickremesinghe said he feared the massacre could trigger instability in Sri Lanka, and he vowed to "vest all necessary powers with the defense forces" to take action against those responsible.

The Archbishop of Colombo, Cardinal Malcolm Ranjith, called on Sri Lanka's government to "mercilessly" punish those responsible "because only animals can behave like that."

The scale of the bloodshed recalled the worst days of Sri Lanka's 26-year civil war, when the Tamil Tigers, from the ethnic Tamil minority, sought independence from the Sinhalese-dominated country. The Sinhalese are largely Buddhist. The Tamils are Hindu, Muslim and Christian.

Sri Lanka, off the southern tip of India, is about 70% Buddhist. In recent years, tensions have been running high between hard-line Buddhist monks and Muslims.

Two Muslim groups in Sri Lanka condemned the church attacks, as did countries around the world, and Pope Francis expressed condolences at the end of his traditional Easter Sunday blessing in Rome.

Six nearly simultaneous blasts took place in the morning at the shrine and the Cinnamon Grand, Shangri-La and Kingsbury hotels in Colombo, as well as at two churches outside Colombo.

A few hours later, two more blasts occurred just outside Colombo, one at a guesthouse where two people were killed, the other near an overpass, Atapattu said.

Also, three police officers were killed during a search at a suspected safe house on the outskirts of Colombo when its occupants apparently detonated explosives to prevent arrest, authorities said.

Authorities said a large bomb had been found and defused late Sunday on an access road to the international airport.

Air Force Group Captain Gihan Seneviratne said Monday that authorities found a pipe bomb filled with 50 kilograms (110 pounds) of explosives. It was large enough to have caused damage to a 400-meter (400-yard) radius, he said.

Harischandra, who witnessed the attack at the Shangri-La Hotel, said there was "a lot of tension" after the bombings, but added: "We've been through these kinds of situations before."

He said Sri Lankans are "an amazing bunch" and noted that his social media feed was flooded with photos of people standing in long lines to give blood.

Meanwhile, the president is expected to declare a nationwide emergency from midnight on Monday following the deadly attacks, the president's office said.