The Australian Greens made the accusation follow news of an incident involving Australian troops in Afghanistan overnight.
The Australian Defence Force (ADF) says the next-of-kin have been notified, and it will release more details at a 9am (AEST) media conference in Canberra.
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The Greens, who want Australia to withdraw its troops from the war, say it is time for a national debate on Australia's involvement in the war.
"The problem with both the major parties on this issue is that they don't want to discuss it," Greens Senator Sarah Hanson-Young told ABC Television.
"The death toll is rising, it is time... to have a good discussion in our parliament about this."
The latest incident follows the deaths of Brisbane-based privates Grant Kirby and Tomas Dale in Oruzgan Province on Friday.
A total of 20 Australian soldiers have been killed in Afghanistan - nine of them since June this year.
