The Australians were military trainers and another two Cambodian soldiers were also wounded, police in Kampong Speu, 50 kilometres from Phnom Penh, said.

Their names have not yet been released.

Police said the mine detonated at a tank base after the Cambodian who was killed picked up the war-era bomb once it was detected under the ground.

Kampong Speu Provincial Governor Vy Samnang told the Phnom Penh Post it was believed the casualties were shooting at targets around 2pm local time on Thursday when they noticed something on the ground.

"He said they went to pick up the object, a Russian-made bomb, which then exploded," The Post reported.

Cambodia is littered with unexploded ordnance (UXOs), a legacy of three decades of civil war. However, casualty figures have steadily come down over the past two decades thanks to an international effort to rid the country of the blight.

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Kampong Speu Provincial Hospital health department director O Vann Then said the three injured people had received "light injuries" to their hands.

"The body of the Cambodian soldier has already been taken out by family while the Australian body is still at the hospital waiting to be taken by the Australian embassy," Vann Then said.

The Australian embassy in Phnom Penh declined to comment. A Cambodian government spokesman was unavailable for comment.

Comment has also been sought from the Australian Defence Force and Department of

Foreign Affairs and Trade.