Officers in Sri Lanka had known of a possible terror plot for weeks before the Easter Sunday atrocity, but the warnings were not heeded.
The nation’s Prime Minister said there will be a probe into why the security services failed to act properly on the information.
He added he and his Cabinet had not been told about the warning.
Police and security chiefs now face mounting criticism.
The warning of terrorist activity first emerged on around April 4.
The PM, Ranil Wickremesinghe, admitted security services had been “aware” of possible attacks.
He said: “We must look into why adequate precautions were not taken.
“Neither I nor the ministers were kept informed.”
The atrocity is said to have been led by an extreme Islamist group in Sri Lanka called National Thowheed Jamath, with support from abroad.
A foreign intelligence agency had learned the NTJ was plotting suicide attacks on churches in Colombo.
On April 11, a week after the initial warnings, police in Sri Lanka reportedly circulated a document entitled “Information of an alleged plan attack” to security chiefs.
Chaos at the heart of the government meant the warnings were never passed on to the Cabinet.
A row between the President and the Prime Minister meant the PM was kept out of security meetings.
Authorities blame the attacks on an international network of extremists with possible links to Islamic State.
At least seven of the attackers used suicide vests, with Christian worshippers targeted.
A Cabinet spokesman said: “All the suicide bombers were local...
“There was an international network without which these attacks could not have succeeded.”
President Maithripala Sirisena will request foreign help to track down those who helped mastermind the plot from abroad.
His office said: “The intelligence reports indicate foreign terrorist organisations are behind the local terrorists. The president is to seek the assistance of the foreign countries.”
Police said 24 people had been arrested after the blasts at churches and hotels.
There was more panic in the capital Colombo yesterday after a suspicious package was found in a van.
Armed police were deployed and officers detonated the package – around 50 yards away from St Anthony’s Church, which was the centre of one of the attacks on Sunday – in a controlled explosion.
There were reports of confusion and chaos as frightened crowds fled the area. It came as footage emerged reportedly showing one of the terrorists going into St Sebastian’s Church in Negombo before the explosion there.
Images show a man wearing a large backpack walking into the building.
Other pictures show what some people say are blood stains on a statue of Jesus at the church.
Police sources have confirmed that the terrorists who targeted the Shangri-La hotel in Colombo had pamphlets and paraphernalia associated with extremist Islamic ideology.
The killers had checked into room 616, where investigators also found two iPhone chargers.
The blast was a result of at least 55lbs of C-4 plastic explosives, though the conclusions await formal confirmation.
Interpol is deploying a team of investigators, including experts in disaster victim identification, to Sri Lanka to assist local authorities.
Workers at the city’s morgue say they faced a grim task in identifying some of the victims.
A curfew was imposed until today, scheduled as a national day of mourning, while the threat of further attacks remains.
Police found 87 bomb detonators at the main bus station in the capital.
The Queen led messages from the Royal Family to express their horror at the atrocity.
Her statement said: “Prince Philip and I were deeply saddened to learn of the attacks in Sri Lanka and send our condolences to the families and friends of those who have lost their lives.
“I pay tribute to the medical and emergency services providing support to those... injured. Our thoughts and prayers are with all Sri Lankans at this difficult time.” Around 200,000 Britons visit the nation each year.
The US State Department said terrorist groups were continuing to plot potential copycat attacks.
It told American citizens that possible targets included tourist locations, transport hubs, shopping malls, hotels, places of worship and airports.
The National Thowheed Jamath was formed in Kattankudy, eastern Sri Lanka, in 2014. It had no history of mass fatality attacks. Sources claim the group had publicly supported IS.
Only monsters would attack worshippers, says journalist Anila Baig
Targeting worshippers on the holiest day in the Christian calendar is beyond heinous and my heart breaks for those who have lost their loved ones.
Pakistan’s PM Imran Khan branded the attacks “horrific”, saying his country stood with Sri Lanka in its hour of grief.
Islam, Christianity and Judaism share many commonalities and people of all three faiths have lived for centuries side by side in communities across the world.
Sri Lanka is a completely multi-cultural country with large numbers of Buddhists, Hindus and Christians. A Sri Lankan government official claims domestic radical Muslim group National Thowheed Jamath carried out the bombings.
And whoever was behind these attacks that ripped through hotels and churches, killing hundreds and injuring many more, the timing could not be more galling.
Just as the atrocities in Christchurch, New Zealand, took place in a mosque during Friday prayers, on the holiest day of the week for Muslims, these multiple attacks on churches and hotels took place on Easter Sunday.
What kind of monsters relish attacking worshippers at prayer?
Coincidentally, the day before Easter Sunday was a significant date for Muslims too as it was Shab e Barat, the holiest night of the year when we believe that past sins will be forgiven and future blessings will be decided.
Many practising Muslims stayed up all night to pray and were fasting yesterday in preparation for the month of Ramadan. It should be a time for soulful reflection, prayer and peace.
As far as I’m concerned no Muslim could commit acts of unprecedented violence like this.
Whoever was behind it, they are not one of us, and we condemn these attacks like all right-thinking people.
The religion of those who have fallen is of no consequence – in a mosque or a church – it only matters that we stand united against all acts of terror.
