CANBERRA, Australia - An Afghan soldier has shot dead his Australian mentor, a puzzling death that Australia's leader said Tuesday would not weaken the nation's commitment to its military role in Afghanistan despite an expected public backlash.

The dead soldier, a 25-year-old army lance corporal, had been on guard duty with his killer at a forward patrol base in the Chora Valley in Uruzgan province on Monday when the Afghan opened fire then fled, officials said.

No details of the killer's motive have been released. He was being hunted by his Afghan National Army colleagues, officials say.

Prime Minister Julia Gillard said the death would puzzle and anger many Australians. She said while hundreds of Afghan National Army soldiers had been trained by the Australian task force, none had ever turned on his mentors before.

"I understand on hard days like this one, the Australian community does question our involvement in Afghanistan _ I think that's very natural and very understandable too," Gillard told Parliament.

"To Australian community members who are asking themselves that question, it is in our nation's interest to continue our deployment to Afghanistan, to see our mission through, to make sure that Afghanistan does not again become a safe haven for terrorist training," she added.

The death was one of two Australian fatalities on Monday that brought Australia's toll in the conflict to 26.

The second fatality was a 27-year-old army lieutenant killed when a Chinook helicopter crashed while on a resupply mission 56 miles (90 kilometers) east of the Australian base in Tarin Kot in Uruzgan.

Australia has 1,550 soldiers in Afghanistan with a primary focus on training an Afghan National Army battalion to take responsibility for security in restive Uruzgan.

Australia, the largest military contributor to the US-led alliance in Afghanistan outside NATO, plans to start withdrawing troops once the Afghan battalion is fully trained as early as next year.

The Greens party, whose support is crucial to Gillard's Labor Party maintaining power, on Tuesday called for Australian troops to withdraw by the end of this year.

"We should bring our troops home safely to our shore to be better deployed in Australia's interests," Greens leader Sen. Bob Brown told reporters as he offered condolences to the families of the latest two fatalities, whose names have not yet been made public.

Australia joined the US-led war against the Taliban in Afghanistan in 2001, but opinion polls show that public support for the campaign has waned over the years as the death toll has mounted and victory proved elusive.