A grieving Australian husband has described the horrific moment he found his wife and daughter dead after a bomb ripped through a Sri Lanka church.

Business manager Manik Suriaaratchi and her 10-year-old daughter, Alexandria, died in an explosion at Negombo, on the west coast of the country, where they were attending an Easter Sunday church service.

Ms Suriaaratchi’s Australian husband, Sudesh Kolonne, was outside when the blast hit and has described the moment a bomb went off during the service.

“I heard a huge noise and I jumped into the church and I saw that my wife and my daughter were on the floor,” he told the ABC.

“I just saw my daughter on the floor and I tried to lift her up, [but] she was already dead. And [then] exactly the same… next my wife is there.”

The family had recently moved back to the island nation after spending decades building their lives and careers in Melbourne.

Australian Sudesh Kolonne mourns the death of his wife and daughter killed in a Sri Lanka church bombing. Photo: ABC

Prime Minister Scott Morrison said it was “unimaginable” how Mr Kolonne would be feeling and he would be getting in contact with the grieving husband and father.

The mother and daughter have been remembered as “beautiful souls”, as police question dozens of terror suspects amid a probe into an “international network” behind the attacks.

Australians Sudesh Kolonne and daughter Alexandra. Photo: Supplied to ABC

Ms Suriaaratchi’s cousin Roshani Suriyaaratchi wrote of her pain: “Can’t find words … devastated.”

“Another loss of a very bright, smart young lady,” work friend Anton Ranaweera wrote in a tribute.

“Informing all our friends about your loss was tough.

“Feel like yesterday the fun times we had back in Sydney. I know you are walking hand in hand with your little one.”

Ms Suriaaratchi was with her daughter in the church while her husband was parking the car, SBS News reported.

The family had previously lived in Australia, and Mrs Suriaaratchi had been managing director of investment company Omega Global.

Mourners gathered in Melbourne on Monday to farewell the mother and daughter before a funeral in Sri Lanka on Tuesday.

Mourner Fahim Mawjood wrote in a tribute that the memories of the victims would “live in our hearts forever”.

“It’s really shocking to know that you are no longer here with us,” Mr Mawjood said.

“You lost your lives on a holy day in a holy place. May your souls rest in peace Manik and Alex.”

Described as an “entrepreneur” on her business website, Ms Suriaaratchi also helped establish a lab to prevent mosquito-borne diseases such as Zika virus and yellow fever in Sri Lanka.

Colleagues lamented the loss of a smart and bright woman. Photo: Facebook

Two other dual-national Australians – women in their late 20s and mid-50s – are among the injured.

One suffered a shrapnel wound, while the other suffered a broken leg.

The news of the impact on Australians came as police in Sri Lanka were interrogating dozens of suspects, as the death toll from the terror attacks rose to 290 by Monday morning.

More than 450 people across the country are being treated for injuries sustained in the eight explosions that seemed to be targeted at Christians celebrating and worshipping on Easter Sunday and tourists.

Another bomb device was also found near the airport in the capital, Colombo, and was destroyed before it could cause harm.

Questions remained about what was done to prevent the attacks,  amid revelations intelligence agencies had prior warning about possible terror plans.

Sri Lanka Cabinet spokesman Rajitha Senaratne said: “We do not believe these attacks were carried out by a group of people who were confined to this country.

“There was an international network without which these attacks could not have succeeded.”

Sri Lankan president Maithripala Sirisena said in a statement the country would seek foreign assistance to track the international links.

Prime Minister Ranil Wickremesinghe acknowledged the government had some prior information about possible attacks on churches involving a little-known local Islamist group. A domestic intelligence report dated April 11 said a foreign intelligence agency had warned Sri Lankan authorities of possible attacks.

Police and locals inspect the damage and fatalities in St Sebastian church at Negombo near Colombo, Sri Lanka. Photo: AAP

The dead included three police officers, who died when a bomb went off as they raided a house looking for suspected terrorists.

Australian tourists caught up in the devastation described seeing blood and dead bodies before being sent back to their hotels for an all-night curfew.

“There were people screaming and dead bodies all around,” Australian man Sam told 3AW radio.

“Kids crying, kids on the ground … I don’t know if they were dead or not.”

Sam said he and a friend were having breakfast at the Shangri-La Hotel when two blasts went off, causing “absolute carnage”.

They had seen two men wearing backpacks seconds before the explosions, he said.

-with agencies