Australia has lost its 23rd soldier in Afghanistan - Sapper Jamie Ronald Larcombe shot dead by insurgents while on patrol in the Mirabad Valley.



The 21-year-old South Australian was part of the same Darwin-based 1st Combat Engineer Regiment which laid Corporal Richard Edward Atkinson to rest last week.



Defence Force Chief Angus Houston said Spr Larcombe and an Afghan interpreter were shot south-east of Patrol Base Wali about 10.30pm Saturday (AEDT).



Despite immediate first aid, neither could be revived.



Their deaths appeared to be the result of a co-ordinated insurgent attack using machine gun and small arms fire.



Air Chief Marshal Houston praised other soldiers on the patrol for fending off the insurgents and providing first aid to the pair, who were quickly evacuated to Tarin Kowt.



Spr Larcombe was described as a dependable, genuine team player who reflected the values of his country upbringing.



"He was a quiet achiever who worked hard and was focused on getting the job done," Air Chief Marshal Houston told reporters in Canberra on Sunday.



"He was also a loyal friend who had a good sense of humour but wasn't interested in being the centre of attention.



"Our nation should mourn the loss of this fine young Australian."



Spr Larcombe, who was halfway through his first tour of Afghanistan, leaves behind his parents, three younger sisters and a girlfriend, who are being given compassionate support by Defence personnel.



He had also served on Operation Padang Assist in 2009, which responded to a devastating earthquake in Indonesia.



ACM Houston said while nothing could match the grief felt by Sapper Larcombe's family, it was another hard day for the army - particularly the 1st Combat Engineer Regiment.



"The unit has lost two of their mates in a very short period of time," he said.



"They are doing it tough but I have great faith in their professionalism, their determination and their ability to support each other as they focus on their mission and also return their former mate home to his family."



ACM Houston said the unit was holding up well considering, and wanted to "prevail" in Afghanistan.



"Their morale is high ... they're good Australian soldiers and they will pull together, they'll mourn together and they'll come out and fight together," he said.



ACM Houston also offered his condolences to the Afghan interpreter's family and paid tribute to his sacrifice.



Defence Minister Stephen Smith said the latest death was another blow to the nation.



"Sapper Larcombe died pursuing his country's national interests," he told journalists in Perth.



"As we pursue our national interest ... to stare down international terrorism, we have to steel ourselves for further fatalities and further casualties."