Sri Lanka's president has vowed to overhaul state security after several bomb blasts on Sunday killed 359 people and wounded about 500.
On Tuesday, Maithripala Sirisena said warnings had not been shared with him and promised "stern action".
The country's Prime Minister Ranil Wickremesinghe said the Islamic State (IS) group may be linked to the blasts.
Funerals are continuing across the country as people try to process last Sunday's attacks.
IS has claimed the attack, although it did not provide direct evidence of its involvement.
Police say they have identified eight out of nine attackers, with no foreigners among them.
"Most of them are well educated and come from maybe middle or upper middle class," Deputy Defence Minister Ruwan Wijewardene said on Wednesday. "They are financially quite independent and their families are quite stable financially.
"We believe that one of the suicide bombers studied in the UK and then later on did his post-graduate in Australia before coming back to settle in Sri Lanka."
In a televised address late on Tuesday, President Sirisena said he would completely restructure the police and security forces in coming weeks.
"The security officials who got the intelligence report from a foreign nation did not share it with me. I have decided to take stern action against these officials."
The BBC World Service's South Asia editor Ethirajan Anbarasan said it was an embarrassing admission by President Sirisena that security officials did not share with him the intelligence report warning about the attacks.
With IS claiming responsibility for the attacks, Sri Lanka is now entering uncharted territory, our correspondent explains.
Authorities say they are looking into possible links between the locals who carried out the suicide bombings and the global jihadist group.
'Grief is all around you'
Rajini Vaidyanathan, BBC News South Asia correspondent, reports from Batticaloa
In the town of Batticaloa, the grief is all around you. Posters of those who died in Sunday's blast hang from every corner. Photos show the young children smiling in party dresses and smart shirts, and written next to their images are their birthdays, as well as the day they died.
They'd been attending Sunday school at the Zion Church, as they did every week. After the service some of them went outside for snacks, a short while later a bomb exploded.
A decade after the civil war ended this community is once again burying its dead. Wreaths of bright pink flowers were left at the freshly dug graves of some of the children. They'd barely been dug - just like the lives lost had barely been lived.
This scenic stretch of the country's east coast has become accustomed to loss. Countless died in the country's civil war. The 2004 tsunami claimed thousands more. Now it's trying to process this latest wave of terror.
Follow @BBCRajiniv for updates from Sri Lanka.
Sri Lanka's government has blamed the blasts on local Islamist group National Thowheed Jamath (NTJ).
But Mr Wickremesinghe said the attacks "could not have been done just locally".
"There had been training given and a coordination which we are not seeing earlier," he said.
Police have now detained around 60 suspects in connection with the attack. A state of emergency remains in effect to prevent further attacks.
The nearly simultaneous attacks targeted three churches packed for Easter services and three major hotels in the capital, Colombo.
An attack on a fourth hotel on Sunday was foiled, Mr Wickremesinghe said. He also warned that further militants and explosives could still be "out there" following the attack.
The country remains tense with police still looking for suspects and possible further explosives.
Who could be behind the attacks?
IS said it had "targeted nationals of the crusader alliance [anti-IS US-led coalition] and Christians in Sri Lanka" via its Amaq news outlet.
It provided no evidence for the claim but shared an image on social media of eight men purported to be behind the attack.
The group's last territory fell in March but even then experts had warned it does not mean the end of IS or its ideology.
Earlier, the country's defence minister Ruwan Wijewardene told parliament that NTJ was linked to another radical Islamist group he named as JMI. He gave no further details.
He also said "preliminary investigations" indicated that the bombings were in retaliation for deadly attacks on mosques in Christchurch, New Zealand, in March.
NTJ has no history of large-scale attacks but came to prominence last year when it was blamed for damaging Buddhist statues. The group has not said it carried out Sunday's bombings.
The Sri Lankan government is facing scrutiny after it emerged the authorities were warned of about a possible attack.
Security services had been monitoring the NTJ but the prime minister and the cabinet were not warned, ministers said.
Who were the victims?
The first mass funeral was held on Tuesday, as Sri Lanka marked an official day of mourning for the victims.
Most of those who died were Sri Lankan nationals, including scores of Christians attending Easter Sunday church services.
Sri Lankan officials said 38 foreign nationals were among the dead, with another 14 unaccounted for. The death toll includes at least eight British citizens and at least 11 Indian nationals.
The mass funeral for about 30 victims took place at St Sebastian's church in Negombo, north of Colombo, which was one of the places targeted in Sunday's blasts. Another funeral service was scheduled for later on Tuesday.
A moment of silence was also observed at 08:30 on Tuesday, reflecting the time the first of six bombs detonated.
Flags were lowered to half-mast and people, many of them in tears, bowed their heads in respect.