Police have now detained around 60 suspects in connection with the attack.
Officials say all of the main suicide bombers were Sri Lankan. The group's Aamaq news agency released an image purported to show the leader of the attackers, standing amid seven others whose faces are covered.
Earlier on Wednesday, Sri Lanka's deputy defence minister Ruwan Wijewardene had said in a press conference that one of the suicide bombers had studied in the UK. "Some of them went overseas for studies", Wijewardene told a news conference.
Referring to an admission by officials that they had missed chances to stop the bombings, he added: 'By now it has been established that the intelligence units were aware of this attack and a group of people were informed. "Foreign partners, including the United Kingdom, are helping us with those investigations". A pair of brothers from a wealthy, upper class family.
The prime minister said some people might lose their job over the intelligence failures.
Nearly 10 years after the end of a brutal civil war between the Tamil Tiger separatist group and the government, Sri Lanka has been plunged into violence yet again.
Pakistani civil society activists hold placards and candles to pay tribute to the Sri Lankan blasts victims, during a vigil in Lahore on April 23, 2019. Until now, Christians had largely managed to avoid the worst of the island's conflict and communal tensions.
CNN reports that the group said via its Amaq news agency that the attacks were carried out by "fighters of the Islamic State", though it provided no evidence.
The Canadian government says the situation remains volatile, and warns other attacks could take place.
The UN said at least 45 children were killed in the attacks.
The Sri Lankan government is now under fire after the Prime Minister admitted intelligence agencies had information that could have stopped the attacks if it had been passed on correctly. "New Zealand has not yet seen any intelligence upon which such an assessment might be based", a spokeswoman for Ardern said in an emailed statement. "They will be used only against terror suspects and I take that responsibility", he said. The warnings were repeated two days and two hours before the attacks, Senaratne said. "The President (Maithripala Sirisena) is planning to make some changes in the security establishments", he said.
Sirisena has said his office never received the Indian report.
More than 1,000 people gathered at St Sebastian's Church in Negombo, north of the capital, which was among those devastated in the blasts, to pay tribute to the dead.
Explosions occurred in eight different locations in Sri Lanka.
Most of those killed and wounded were Sri Lankans, although officials said 38 foreigners were also killed. Author of "Pain, Pride, and Politics: Social Movement Activism and the Sri Lankan Tamil Diaspora in Canada".
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