An Australian mother and her 10-year-old daughter are among 290 people killed in terrorist attacks on churches and luxury hotels in Sri Lanka.

Key points: Up to 290 people were killed in bombings at churches and luxury hotels across Sri Lanka

Up to 290 people were killed in bombings at churches and luxury hotels across Sri Lanka Scott Morrison said two of those killed were Australian, and two other Australians were among hundreds injured

Scott Morrison said two of those killed were Australian, and two other Australians were among hundreds injured A Sri Lankan investigator said the bombings were carried out by seven suicide bombers

Manik Suriaaratchi and her daughter Alexendria lost their lives when a bomb exploded inside a church in Negombo, according to SBS.

At a vigil in Melbourne, Fahim Mawjood told SBS that the family had travelled back to Sri Lanka a few years ago to care for a relative.

He said he had spoken to Ms Suriaaratchi's husband, who was uninjured in the blast as he was parking the family car when the bomb went off.

Manik Suriaaratchi and her 10-year-old daughter Alexendria were killed in the Sri Lanka terror bomb blasts. ( Facebook: Fahim Mawjood )

In a Facebook post to the deceased mother and child, Mr Mawjood said it was "really shocking" they were no longer here.

"You lost your lives on a holy day in a holy place. The sweet memories of Alex and yours will live in our hearts forever. May your souls rest in peace Manik and Alex," he wrote.

Friends in Australia have started paying tribute to Manik Suriaaratchi and her daughter Alexendria on social media. ( Facebook: Lucien Pereira )

Prime Minister Scott Morrison has confirmed two Australians were killed and that both victims were members of the same family and were living in the country at the time.

"We deeply regret these deaths and we extend our deepest and most sincere sympathies to the family," he said.

"As the days pass and the injured are treated and some of them succumb to their wounds, we are seeing this massacre go from what was bad, very bad, to much, much worse."

Alexendria smiles at the camera in this family photo taken in 2015. ( Facebook )

The Department of Foreign Affairs and Trade said it would not comment further "out of respect for the privacy of the family".

Two other Australians, both women, one in her 50s and the other in her 20s, are among hundreds of people who were injured in the Easter Sunday attacks.

Manik Suriaaratchi pictured with Australian Defence Force personnel during Mount Lavinia Beach clean up in March 2019. Ms Suriaaratchi worked with Omega Global Sri Lanka, one of the partners in the clean up campaign. ( Facebook )

Mr Morrison said one woman received shrapnel wounds and the other suffered a broken leg.

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Earlier on Monday Sri Lankan authorities confirmed the death toll from the attacks had risen to 290, with around 500 injured.

The coordinated bombings were carried out by seven suicide bombers, Sri Lankan government forensic crime investigator Ariyananda Welianga said.

He said most of the attacks were carried out by lone bombers, but said two attackers struck at Colombo's Shangri-La Hotel.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 1 minute 9 seconds 1 m 9 s Sri Lanka's capital was rocked by explosions set off during Easter Sunday services ( ABC News )

Authorities also confirmed on Monday they had "prior information" of an imminent attack on churches, up to 10 days before the bombings.

Two government ministers have alluded to intelligence failures.

Telecommunications Minister Harin Fernando tweeted: "Some intelligence officers were aware of this incidence. Therefore there was a delay in action. Serious action needs to be taken as to why this warning was ignored."

He said his father had heard of the possibility of an attack as well and had warned him not to enter popular churches.

And Mano Ganeshan, the minister for national integration, said his ministry's security officers had been warned by their division about the possibility that two suicide bombers would target politicians.

The police's Criminal Investigation Department, which is handling the investigation into the blasts, will look into those reports, police spokesman Ruwan Gunasekara said.

St Sebastian's Church was damaged in blast in Negombo, north of Colombo. ( AP: Chamila Karunarathne )

Bombers were Sri Lankan citizens from militant group

Earlier, Sri Lanka's Defence Minister Ruwan Wijewardena described the blasts as a terrorist attack by religious extremists.

Police said 13 suspects had been arrested.

On Monday a government official said domestic militant group National Thowfeek Jamaath was responsible.

All of the bombers were Sri Lankan citizens, but authorities suspect foreign links, Health Minister Rajitha Senaratne said.

News outlet Agence France-Presse (AFP) reported it had seen documents showing that Sri Lanka's police chief Pujuth Jayasundara issued an intelligence alert to top officers 10 days ago, warning that suicide bombers planned to hit "prominent churches".

"A foreign intelligence agency has reported that the NTJ [National Thowheeth Jama'ath, a radical Muslim group in Sri Lanka] is planning to carry out suicide attacks targeting prominent churches as well as the Indian high commission in Colombo," the alert said, according to AFP.

Cardinal Malcolm Ranjith, the archbishop of Colombo, said the attacks could have been thwarted.

"We placed our hands on our heads when we came to know that these deaths could have been avoided. Why this was not prevented?" he said.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 19 seconds 19 s Sri Lanka's Prime Minister condemns those responsible for deadly blasts ( ABC News )

Prime Minister Ranil Wickremesinghe said there was not an adequate response and there needed to be an inquiry into how the prior information of the attack, which was not shared with ministers, was used.

The Tamil Tigers, once a powerful rebel army known for its use of suicide bombers, was crushed by the government in 2009, and had little history of targeting Christians.

While anti-Muslim feeling has swept the island in recent years, fed by Buddhist nationalists, the island has no history of violent Muslim militants.

The country's small Christian community has seen only scattered incidents of harassment in recent years.

ABC/wires