The identities of some of the 250 Australian and British soldiers discovered in an unmarked World War One mass grave at Fromelles in France have been confirmed, Sky News Australia reported Tuesday.

Prime Minister Kevin Rudd on Tuesday backed media reports that said 75 of the 250 have had their identities confirmed some 90 years later thanks to DNA testing.

The move capped a two-year search and recovery mission to identify the WWI soldiers' names and find them an appropriate resting place.

Rudd said the latest news was momentous.

'The discovery of these remains and the work to identify them and to rebury them in a fitting commonwealth cemetery has been an important task,' he told parliament on Tuesday.

'Obviously to the families involved this will be momentous news and we'll make a public statement once all the families have been contacted.'

The 1916 Battle of Fromelles was the costliest in Australian military history, with 5,533 soldiers either killed, wounded, taken prisoner or missing.

A group of them was recovered by German soldiers and buried in an unmarked mass grave found near Pheasant Wood on the outskirts of Fromelles in northern France.

The Australian and British government worked to rebury them, with the final soldier re-interred at a new military cemetery last month.

The government then embarked on a thorough DNA testing process, gathering samples from almost all of the 250 soldiers, which they then ran against samples provided by family members.

Veterans' Affairs Minister Alan Griffin is expected to make a formal announcement on the identities on Wednesday.

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