CANBERRA: Australia has sustained its first combat casualty in Afghanistan or Iraq after a roadside bomb killed a soldier in southern Afghanistan, the country's military chief said Tuesday.

The soldier, whose name and rank were not immediately released, was killed Monday when an improvised explosive device went off near the armored vehicle he was driving, Air Chief Marshal Angus Houston told reporters in Canberra. Another soldier was seriously injured in the attack.

``This is a tragic day for the Australian Defense Force and our thoughts and prayers are with the families of these two soldiers,’ Houston told reporters in the capital, Canberra.

``We're now working on arrangements to bring the body of the fallen soldier back to Australia.''

The soldier's death comes as Australia prepares for general elections due to be called anytime in the next few weeks.

Polls show conservative Prime Minister John Howard facing a landslide defeat amid rising opposition to Australia's involvement in Iraq and Afghanistan.

Howard has refused to set a timetable for withdrawing Australian troops from either conflict, saying they will remain for as long as they are needed.

But the soldier's death is likely to increase calls for a phased Australian withdrawal, as a recent survey by the government-funded U.S. Studies Center found that as many as 64 percent of Australians oppose the Iraq war, and 51 percent oppose Australia's involvement in Afghanistan.

Howard, a staunch U.S. ally, was among the first leaders to send troops to Afghanistan after the Sept. 11, 2001 attacks on New York and Washington. He defended Australia's involvement in the conflict as ``a just cause.''

``The operation in Afghanistan involves resisting brutal terrorism, it's a just cause and this soldier was part of an Australian contribution to that just cause,'' he told reporters.

Australia maintains around 1,000 troops in Afghanistan and 1,500troops in and around Iraq, but had not lost any soldiers from direct enemy attacks until now. An Australian soldier accidentally shot himself in his Baghdad barracks last year, and several Australians have been wounded in clashes with the Taliban over recent months.

Australia's involvement in Iraq is a key policy difference between Howard and opposition leader Kevin Rudd, who opinion polls show is heading for a decisive victory.

Rudd says he will bring Australia's roughly 550 combat troops home from Iraq in a phased withdrawal, leaving about 1,000 others in support and training roles.