Acting Chief of Defence Force Lieutenant-General David Hurley said the soldier from 4thBattalion, Royal Australian Regiment, who was not officially named last night, had been on foot when the bomb exploded. He died in the blast.

He is the seventh Australian soldier to have died in Afghanistan.

General Hurley said the blast wounded two other soldiers, but they had since returned to duty.

The explosion took place in the middle of the night in Afghanistan, early yesterday morning Canberra time. The men were part of an offensive against the Taliban in Oruzgan, the dangerous southern province where most of Australia's 1090 soldiers are based.

''The soldier was intimately involved in ongoing Australian Special Forces operations to neutralise and fracture the Taliban insurgency's leadership in Oruzgan province,'' General Hurley said.

He would not reveal further details last night because the mission was continuing, but said an inquiry into the soldier's death would be issued when the operation was completed.

''Releasing further information on this incident could jeopardise [the task group's] safety and the safety of those still engaged in supporting them,'' he said.

Prime Minister Kevin Rudd said he was deeply saddened to learn of the death. ''I'm sure I'm speaking on behalf of all Australians when I say that our deepest sympathies are with this young man's family, his friends and his colleagues.''

There were no plans to increase the number of troops in Afghanistan because of the latest casualty.

''Our troops in Afghanistan are engaged in dangerous work. They are engaged in important work, and they perform their role with distinction and with dedication, with bravery and with professionalism.''

Opposition Leader Malcolm Turnbull added his prayers, saying the soldier and his colleagues were on the front line of the battle against terrorism.