-- Death toll from Sri Lanka blasts rises sharply to 290

-- US advisory warns more attacks are possible

-- Blasts hit churches, hotels 10 years after end of civil war

-- President calls National Security Council meeting

-- Military find roadside bomb at Colombo's airport

Seven suicide bombers took part in the attacks on churches and luxury hotels in Sri Lanka that killed 290 people and wounded more than 500, an investigator said on Monday, while a government spokesman said an international network was involved.

Two of the suicide bombers blew themselves up at the luxury Shangri-La Hotel on Colombo's seafront, said Ariyananda Welianga, a senior official at the government’s forensic division. The others targeted three churches and two other hotels.

A fourth hotel and a house in a suburb of the capital Colombo were also targeted, but it was not immediately clear how those attacks were carried out.

"Still the investigations are going on," Welianga said.

There was no claim of responsibility for the Easter Sunday attacks, which mainly took place during church services or when hotel guests were sitting down for breakfast buffets.

"Guests who had come for breakfast were lying on the floor, blood all over," an employee at Kingsbury Hotel, one of those targeted, told Reuters.

"We just picked up everyone, dead or alive and evacuated them."

Cabinet spokesman Rajitha Senaratne said an international network was involved, but did not elaborate.

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

The president, Maithripala Sirisena, said in a statement the country will seek foreign assistance to track the international links.

Prime Minister Ranil Wickremesinghe acknowledged on Sunday that the government had some prior information about possible attacks on churches involving a little-known local Islamist group.

A domestic intelligence report dated April 11 and seen by Reuters said a foreign intelligence agency had warned Sri Lankan authorities of possible attacks.

Four of the bombs went off at roughly the same time on Sunday, at 8.45 am, with two others coming within 20 minutes. The explosions at the fourth hotel and the house were in the afternoon.

Most of the dead and wounded were Sri Lankans although government officials said 32 foreigners were killed, including British, US, Turkish, Indian, Chinese, Danish, Dutch and Portuguese nationals.

Denmark's richest man Anders Holch Povlsen and his wife lost three of their four children in the attacks, a spokesman for Povlsen's fashion firm said.

The US State Department said in a travel advisory "terrorist groups" were continuing to plot possible attacks in Sri Lanka and targets could include tourist spots, transport hubs, shopping malls, hotels, places of worship, airports and other public areas.

The government announced a curfew in Colombo from 8 pm until 4 am

Separately, the president said a nationwide emergency will go into effect at midnight local time on Monday, granting police and the military extensive powers to detain and interrogate suspects without court orders.

SECTARIAN VIOLENCE

There were fears the attacks could spark a renewal of communal violence, with police also reporting late on Sunday there had been a petrol bomb attack on a mosque in the northwest and arson attacks on two shops owned by Muslims in the west.

Buddhist-majority Sri Lanka was at war for decades with ethnic minority Tamil separatists but violence had largely ended since the government victory in the civil war, 10 years ago.

Sri Lanka's 22 million people include minority Christians, Muslims and Hindus.

Police said on Monday that 24 people had been arrested, all of whom were Sri Lankan.

The Sri Lankan military, who were clearing the route from Colombo airport late on Sunday in preparation for the return of President Sirisena from an overseas visit, found a crude bomb near the departure gate, an air force spokesman said.

They destroyed the device in a controlled explosion.

Traffic was uncharacteristically thin in normally bustling Colombo after an island-wide curfew was lifted earlier Monday.

Soldiers with automatic weapons stood guard outside major hotels and the World Trade Centre in the business district, where the four hotels were targeted, a Reuters witness said.

Scores of people who were stranded overnight at the main airport began making their way home as restrictions were lifted.

The government also blocked access to social media and messaging sites, including Facebook and WhatsApp, making information hard to gather.

Victims of the attacks included a British mother and son at breakfast at the Shangri-La, British media reported.

An Australian survivor, identified only as Sam, told Australia's 3AW radio the hotel was a scene of "absolute carnage".

He said he and a travel partner were having breakfast at the Shangri-La when two blasts went off. He said he had seen two men wearing backpacks seconds before the blasts.

"There were people screaming and dead bodies all around," he said. "Kids crying, kids on the ground, I don't know if they were dead or not, just crazy."

There were similar scenes of carnage at two churches in or near Colombo, and a third church in the northeast town of Batticaloa, where worshippers had gathered for Easter Sunday services. Pictures from the scene showed bodies on the ground and blood-spattered pews and statues.

Dozens were killed in one of the blasts at the Gothic-style St. Sebastian church in Katuwapitiya, north of Colombo. Police said they suspected that blast was a suicide attack.

DOMESTIC FEUD

Questions over why the intelligence report was not acted upon could feed into a feud between the prime minister and the president.

Sirisena fired the premier last year and installed opposition strongman Mahinda Rajapaksa in his stead. Weeks later, he was forced to re-instate Wickremesinghe because of pressure from the Supreme Court but their relationship is still fraught as a presidential election nears.