The government is now investigating possible links to worldwide terrorist organisations as well.
Colombo, the seaside capital of the Indian Ocean island, was still jittery on Monday.
A woman is helped after she collapsed as silence is observed as a tribute to victims of the attacks in Sri Lanka on Tuesday. The Prevention of Terrorism Act permits the authorities to detain suspects for months, and often years, without charge or trial, facilitating torture and other abuse. "The streets are deserted, the mood is forlorn and it seems like everyone is asking the question, 'Why us?'"
"There was a bomb blast, I heard a huge noise and I jump into the church and I saw that my daughter and my wife was on the floor", he told ABC from Colombo. "There are people outside the city's main hospitals, they're still looking for their loved ones".
US intelligence sources said the attacks carried some of the hallmarks of the Islamic State extremist group, although they were cautious because the group had not claimed responsibility. As of Monday, at least 24 people were detained in connection with the attacks. "Serious action need to be taken as to why this warning was ignored", Fernando said.
"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 global 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 worldwide links.
Sri Lankan prime minister Ranil Wickremesinghe also acknowledged that there was prior information, but he was not informed about it. Weeks later, he was forced to re-instate Wickremesinghe because of pressure from the Supreme Court and their relationship is still fraught as a presidential election nears.
Rohan Gunaratna, a Singapore-based security expert, said the Sri Lankan group is Daesh's branch in Sri Lanka and perpetrators were known to have links to Sri Lankans who travelled to join the hardline group in Syria and Iraq. The three hotels and one of the churches, St. Anthony's Shrine, are frequented by foreigners.
"Still the investigations are going on", Welianga said.
It was the first major attack since the end of a civil war 10 years ago.
Sri Lanka's 22 million people include a majority Buddhist community as well as minority Christians, Muslims and Hindus.
Most of the dead and wounded were Sri Lankans, although government officials said 32 foreigners were killed. As officials respond to this crisis, they should use their authority to ensure access to essential and long-term medical services for the victims, Human Rights Watch said.
While almost all the victims were Sri Lankan, people from eight countries were killed, including three of the four children of a Danish billionaire.
DENMARK: The Bestseller clothing chain confirmed Danish media reports that three of the children of its owner, business tycoon Anders Holch Povlsen, were killed in the attacks.
UNITED STATES: The State Department says at least four Americans were killed and several others seriously injured.
Sam wasn't hurt, thankfully, telling 3AW he was about "5 to 10 metres away" from the initial blast.
He said he and a travel partner were having breakfast at the Shangri-La when two blasts went off.
Footage on CNN showed what it said was one of the bombers wearing a heavy backpack.
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.
While no official party has come forward to admit to the attacks, police have reportedly apprehended 13 suspects.