Police are checking vans and lorries and have been ordered to be vigilant after a tip off that vehicles carrying explosives have entered Colombo city, a police source told The Independent.

An eye witness said police were investigating a suspicious vehicle close to the Taj Hotel, which is understood to have been one of the intended targets on Sunday.

It comes after the army's bomb squad detonated a van outside St Antony's church in the capital on Monday, sparking fresh panic among the crowd of people gathered outside to pay their respects.

The senior police source, who asked not to be named because he was not authorised to speak on the matter, said the threat to Sri Lanka was "far from over". Government schools, which were due to open on Wednesday, have been ordered closed until next week.

The death toll from the Easter Sunday bombings in Sri Lanka has risen to 311, including eight Britons and dozens of other foreign tourists, as the government faces growing questions over its failure to prevent the attacks.

The government is expected to make a formal statement on Tuesday regarding the perpetrators of the attack, though some ministers have already suggested the recently formed National Thowheed Jamaat militant group is to blame.

Sri Lanka observed three minutes of silence at 8.30am, 48 hours after the coordinated attack that hit three major Catholic churches and three international hotels.

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

The country is also holding a national day “to mourn the senseless loss of innocent lives”, the prime minister’s office said in statement.

With so many hundreds injured in the attacks, there is every indication that the death toll will rise further.

At the main Colombo National Hospital alone, a health official who asked not to be named told The Independent that more than 260 patients were admitted following the blasts on Sunday.

Other hospitals also took in the wounded, including many at the Negombo Base Hospital near St Sebastian’s Church in the northern town of Negombo, which also suffered many casualties.

The health official said many of those wounded suffered severe burns and head injuries. He said 15 brain surgeries had been carried out on Monday alone, and that many of the patients would not survive.

One patient, Buddika Dinesh, told The Independent he had been working in the restaurant at the five star Kingsbury hotel when it was hit by an explosion. He did not see the suicide bomber himself.

“There was a blast, and I was knocked over. When I opened my eyes, everyone was down.”

Mr Dinesh was hit by flying debris in five places, including his chest, arm and just below his eye. He said he believes three people were killed on the spot.

“One of them was my colleague. I am not angry about what happened, I am sad, so sad for him.”

One line of inquiry will be asking what intelligence services knew about the attack.

Sri Lanka’s health minister Rajitha Senaratne has claimed Sri Lankan authorities received warnings about a potential terror attack weeks before the bombings.

The politician said the defence ministry wrote to the police chief with intelligence that included the group’s name on 9 April.

Two days later, police wrote to the heads of security of the judiciary and diplomatic security division, he said.

Minister for Telecommunications Harin Fernando also tweeted: “Some intelligence officers were aware of this incidence.

“Therefore there was a delay in action. What my father heard was also from an intelligence officer.

“Serious action need to be taken as to why this warning was ignored.”

Video shows moment van explodes in Colombo, Sri Lanka

Members of three British families were among those killed on Easter Sunday.

Lawyer Ben Nicholson lost his wife Anita, son Alex, 14, and daughter Annabel, 11, when one of seven suicide bombers struck as they ate breakfast at the Shangri-La hotel in Colombo.

Londoner Matthew Linsey’s daughter Amelie, 15, and son Daniel, 19, were killed in the same blast on the final day of their holiday.

GP Sally Bradley and her husband Bill Harrop, a retired firefighter from Manchester, died in the Cinnamon Grand Hotel bombing.

It emerged on Monday that Danish billionaire Anders Holch Povlsen lost three of his four children in the attacks.

Mr Holch Povlsen is the largest stakeholder in online fashion retailer Asos and is believed to be the largest private landowner in Scotland after buying a string of estates.