Australians mourned Indian Ocean tsunami victims on Sunday, with national flags flowing at half mast, special services being held and silence observed across the country.

In a unique way to mark the National Day of Mourning and Reflection for the 160,000 victims, thousands of Australian surfers gripped each other in beach waters and formed rings of remembrance for the disaster victims.

A total of 30 rings of remembrance were made in the states of Western Australia, South Australia, New South Wales and Queensland.

"The whole beach-going community is rallying behind this great opportunity to show unified support and express grief for the victims of the tsunami," said chairman of the Surfrider Foundation of Australia, Geoff Withycombe.

Special church services were held across the country. Australia's political leaders, including Prime Minister John Howard, gathered at Sydney's St Andrew's Anglican Cathedral for a service. Howard attended another mosque service for the same purpose last Friday.

Governor General Michael Jeffery said in a statement Sunday that the tsunami has united the world "in a spirit of unprecedented generosity."

"Today Australians mourn together. Tomorrow we continue to rebuild," he said.

About 4,000 West Australians of all ages and nationalities gathered on the shores of the Indian Ocean Sunday morning for a multi-faith memorial service.

In South Australia, Premier Mike Rann used the mourning to pay tribute to the medical staff helping victims of the tsunami.

The nearly 1,000 Australian troops in Indonesia on tsunami relief mission also stopped work briefly to pay respects to victims of the disaster.

The Indonesian ambassador to Australia, Imron Cotan, described the national event as "a great source of consolation and strength for the survivors of this horrific tragedy."

He issued a statement to thank Australia for its aid, saying it "demonstrates clearly that both countries are able and eager to work together."

The Australian government has pledged 1 billion dollars (0.77 billion US dollars) in aid for Indonesia, and Australians have donated about 200 million dollars (154 million US dollars).