Prime Minister Scott Morrison has condemned the "devastating" bomb blasts in Sri Lanka and says it's still unclear if any Australians are among the 138 dead and 400 injured in the Easter Day attack on the churches and hotels.
The Australian government is now making "urgent" inquiries to reach people in the capital city, Colombo, where several of the terror attacks took place.
Nine foreigners are believed to be among the dead from the blasts at three churches and three hotels: Shangri-La Colombo, Kingsbury Hotel and Cinnamon Grand Colombo.
"The devastating nature of this horrific attack on innocent lives, simply going about their day, going to worship on the holiest of days of the Christian calendar, is just absolutely devastating," Mr Morrison told reporters at Kirribilli House on Sunday.
"There are many Australians regularly travelling in Sri Lanka and our mission in Colombo will be following through on the safety of those Australians."
The staff at the mission have been confirmed safe but the information coming out of Colombo is "confused", the prime minister said, and it's still unclear if any Australians have been caught up in the six blasts.
"I'm sure the information will become even more sickeningly real," he said.
Australia's Catholic leadership pledged to rally around their Sri Lankan counterparts in Australia and abroad following the attack.
"This attack has something demonic about its planning and execution," Australian Catholic Bishops Conference president Archbishop Mark Coleridge said in a statement.
"We also know that violence like this won't have the last word. That's what Easter is about."
The Department of Foreign Affairs and Trade is now working to firm up the information as it relates to Australian travellers.
"Following several bomb blasts in Sri Lanka, the Australian High Commission in Colombo is making urgent enquiries with local authorities to determine the welfare of any Australians affected," a DFAT spokeswoman said in a statement to AAP on Sunday.
The spokeswoman said anyone concerned about friends and family in Sri Lanka should contact their loved ones directly and, if that fails, contact DFAT.
The prime minister and opposition leader Bill Shorten are both receiving briefings from the department.
Mr Shorten said the news was "devastating".
"We think also of Australia's beloved Sri Lankan community who will carry an immense sense of shock and sadness today," he wrote on Twitter on Sunday.
There were no immediate claims of responsibility for the attacks in a country which was at war for decades with Tamil separatists until 2009 during which bomb blasts in the capital were common.
"Sri Lanka hasn't seen this form of violence since 2009 when hostilities ceased in that country," Mr Morrison said.
"We do know that innocent lives have been stolen once again."
Former prime minister Malcolm Turnbull also took to Twitter to share sympathy for the victims.
"The peace of Easter shattered by the senseless and cowardly attacks on Christian worshippers in Sri Lanka," he wrote on Sunday.
"We send our love and sympathy to the families of the victims and pray the injured have a speedy recovery."
Crowds of hundreds are flooding Colombo hospitals to give blood, Sri Lankan social media accounts showed on Sunday evening.
Australian Associated Press