Two Australians including a 10-year-old girl have been killed in the Sri Lanka bomb blasts and another two have been injured.
Prime Minister Scott Morrison has confirmed the deaths, as the number of people believed to be killed in the attacks has risen to at least 290.
"Right now, Sri Lanka is grieving, Australia is grieving," Mr Morrison told reporters in Melbourne.
"Two Australians have lost their lives in this terrible massacre and my heart is full of grief for them and their families."
While Mr Morrison did not go into details, SBS reported on Monday the dead were an Australian mother and her 10-year-old daughter who were attending a church service in Negombo.
SBS said the mother, Manik Suriaaratchi, and her daughter Alexendria had returned to Sri Lanka several years ago to look after a family member, according to a friend of the family.
The prime minister confirmed another two Australians – both of whom were dual citizens – have been injured but are in a stable condition.
One has been treated for shrapnel wounds and the other a broken leg, with both receiving consular support.
Mr Morrison said it was too early to say whether more Australians could be among those who have been hurt.
"As the days pass, and the injured are treated, and some of them succumb to their wounds as well, we are seeing this massacre going from what was bad, very bad, to much, much worse," he said.
More than 500 people have been injured in the bomb blasts that ripped through three churches, three luxury hotels and a guesthouse on Easter Sunday.
The Australian High Commission in Sri Lanka has been working to determine the whereabouts of Australians and monitor the situation.
Australia's travel advice for Sri Lanka has been upgraded to "reconsider your need to travel" in the aftermath of the attack.
DFAT says Australians concerned for family or friends should try to contact them directly before contacting the consular emergency centre.
Labor leader Bill Shorten described the attacks as devastating.
"It is unthinkable that people at prayer should be the subject of this cowardly terror attack," Mr Shorten said.
"We stand with Sri Lankan Australians, they're a mighty community, and we stand with Sri Lanka."
Mr Morrison earlier said the nation's hearts went out to its brothers and sisters in Sri Lanka.
"We are full of love because love conquers fear. Love conquers evil. Love is the basis of peace and it's what binds us all together as Australian people," he said.
Six bombs were detonated simultaneously at three churches and three luxury hotels popular with tourists on Easter Sunday, authorities said.
Seven suicide bombers responsible
At least 290 people were killed and more than 500 people were injured in the bombings about 8.45am (local time), according to hospital and police officials.
The Prime Minister said it was too early to say all Australians were accounted for.
The bombings were carried out by seven suicide bombers, a government investigator said Monday.
An analysis of the attackers’ body parts made clear that they were suicide bombers, said Ariyananda Welianga, a forensic crime investigator.
He said most attacks were by one bomber, with two at Colombo’s Shangri-La Hotel.
Meanwhile, Sri Lankan police investigating the bombings are examining reports that intelligence agencies had warnings of possible attacks, officials said Monday.
At the Shangri-La Hotel, a witness said “people were being dragged out” after the blast.
“There was blood everywhere,” said Bhanuka Harischandra a 24-year-old from Colombo and founder of a tech marketing company.
He was heading to the hotel for a meeting when it was bombed.
“People didn’t know what was going on. It was panic mode.”
Most of those killed were Sri Lankans. But the three bombed hotels and one of the churches, St. Anthony’s Shrine, are frequented by foreign tourists, and Sri Lanka’s Foreign Ministry said the bodies of at least 27 foreigners from a variety of countries were recovered.
The US said “several” Americans were among the dead, while Britain, India, China, Japan and Portugal said they, too, lost citizens.
Do you have a story tip? Email: firstname.lastname@example.org.