An Australian soldier was killed by an improvised explosive device in Afghanistan during a mission against insurgents, military officials said on Monday.

The 24-year-old's death brought to 39 the number of Australian lives lost in the conflict.

"The soldier was clearing a compound when an IED detonated, killing him instantly," Australian defence chief General David Hurley said.

"No other Australian or Afghanistan personnel were killed or wounded in the incident.

"The special operations mission remains ongoing so I cannot provide specific details about the location or the mission itself without risking the safety of this young man's comrades."

Australia is a close ally of the United States and its Afghan deployment began in 2001. It announced this year that it would begin withdrawing its forces in 2013, earlier than planned due to significant security gains.

Most of the 1,550 Australian troops in Afghanistan are based in Uruzgan province, with a focus on training and mentoring Afghan National Army soldiers.

Prime Minister Julia Gillard, who visited troops in Afghanistan a week ago, said morale remained good and the country was committed to the timetable of handing over responsibility to Afghans forces in 2014.

"Having just been in Afghanistan, I can say that our troops there are in good spirits. Their morale remains high even though during the course of this year they have seen a great deal of loss," she said.

"They are very determined to see the mission that we have set ourselves through, a mission with a defined strategy and a defined end point."