Australians marked the first anniversary of devastating wildfires that killed 173 people, grieving for those who lost their lives and praying for the survivors in a national day of mourning yesterday.

The "Black Saturday" bushfires, Australia's worst natural disaster, wiped out entire towns and destroyed more than 2,000 homes as they swept through the southeastern state of Victoria. Twenty-three of the dead were children.

"One year ago our lives changed forever," one woman, who lost her son and her home in the inferno, told a memorial service in Melbourne.

"On that day we lost our past, our present and our future.

"To all of those who have lost your homes, your businesses, your pets, your memories, we feel your pain. To all those who grieve for family, friends and neighbours, you share my pain," she said.

As flags across Australia flew at half-mast, a minute's silence was observed at a memorial service at Melbourne's St Paul's Cathedral attended by Prime Minister Kevin Rudd.

Mourners hugged each other as they listened to music and readings from the Bible and candles were lit to honour the communities affected.

"February 7 will be forever etched in the nation's memory as a day of mourning but also one of tremendous spirit and inspiration," Mr Rudd said ahead of the service.

"Our thoughts today are with the survivors of the bushfires as they remember the people they lost and work to rebuild their lives and towns. Their quiet courage has inspired a nation."

In the worst affected towns of Marysville, Kinglake and Strathewen smaller services and events were held to remember those lost.

In Marysville, bereaved father Rod Liesfield spoke of his anguish at surviving fires that took the lives of his wife and two sons, aged 12 and 14.