An Australian special forces soldier has been killed in Afghanistan.

The death takes the toll to 18 since Australian troops first went to Afghanistan in late 2001.

Seven of the soldiers killed were this year.

Acting Defence Force chief Lieutenant General David Hurley named the soldier as Trooper Jason Brown, 29, a member of the Perth-based Special Air Service Regiment.

He says several insurgents engaged the coalition troops using small arms and Trooper Brown suffered multiple gunshot wounds.

Lieutenant General Hurley has expressed deep regret at the death.

Lieutenant General Hurley said no other other Australian or Afghan troops were wounded.

He said the soldier's family had been notified.

Lieutenant General Hurley said Trooper Brown was an experienced soldier with just over 10 years service. This was his first deployment to Afghanistan but he had deployed three times to East Timor.

"Australian troops are constantly engaged in this battle. They face significant threats every day and do so with professionalism and courage," he told reporters.

"It is these characteristics which make Australian service personnel so well regarded around the world.

"When a member of the ADF family dies in the service of our country, it hits us all very hard."

Trooper Brown was not married and had no children.

Lieutenant General Hurley declined to comment further on the fatal incident, which occurred at 3.30am on Saturday NZT time, because the operation is ongoing and troops are still out in the field.

He said Defence would work to repatriate Trooper Brown's body within the week, but it could not yet be confirmed if that timeframe was possible.

Defence Minister John Faulkner said he had earlier on Saturday spoken to Prime Minister Julia Gillard and Opposition Leader Tony Abbott about Trooper Brown.

Senator Faulkner said the nation's thoughts were with Trooper Brown's family and with his fellow soldiers in Afghanistan.

"We cannot ease their grief any more than we can repay his sacrifice," he said.

In country NSW, Ms Gillard extended the nation's sympathy to the family and friends of Trooper Brown.

''We have lost a brave soldier, we have lost Trooper Jason Brown,'' she said.

''Of course this is tragic news for our nation but the grief that we feel is so much less than the devastation that will be felt by his family and friends.''

Despite the death of Trooper Brown Ms Gillard reaffirmed her commitment to Australia's role in the country.

''I am determined to see the mission through because that's in the best interests of the Australian people,'' she said.

Ms Gillard said Afghanistan had been a ''safe haven for people who would seek to take the lives of Australians''.

The Prime Minister would not speculate on the funeral arrangements, but said if the service was next week she expected both she and Mr Abbott would attend and suspend campaigning for the day.

Speaking from Trooper Brown's hometown Perth, Mr Abbott also expressed his sympathy.

But he echoed Ms Gillard's support for Australia's mission in Afghanistan.

"I think the important thing is to achieve our mission,'' Mr Abbott said.

''Our mission is to try to ensure that there is a stable government in Afghanistan and our mission is to try and ensure that the Afghan army in Oruzgan province is in a fit and proper state to maintain security there."

Senator Faulkner said recent months had been a time of increasing danger in Afghanistan.

He said Australian defence personnel continued to carry out their work with courage and professionalism in conditions of real hardship and very real danger.

"I can assure Jason's family and friends that he, together with his mates, were striking at the heart of the Taliban insurgency as part of our mission in Afghanistan to make sure that extremists and international terrorist groups do not again find safe havens and training grounds in that country," he said.

"This is a critical time for the international coalition in Afghanistan and for the Afghan people.

"The work of pushing back the Taliban is difficult, it is costly, but it is absolutely necessary if we are to achieve our goals in Afghanistan."

Senator Faulkner and Lieutenant General Hurley were speaking at a news conference at Defence headquarters in Canberra.

- with AAP, Dan Harrison, Dylan Welch