The men suffered serious wounds but all were in a stable condition after an Afghan National Army soldier opened fire with an automatic weapon and a grenade launcher at a joint base at Charmistan in Uruzgan province on Tuesday.
Two Afghan soldiers were also wounded before the man fled in an Afghan army vehicle.
The incident comes less than a fortnight after another Afghan soldier killed three Australians and wounded seven others when he opened fire during a parade in Kandahar province.
"It is too early to speculate that the two incidents are linked," defence force chief David Hurley told reporters, adding that nine or 10 Australians and about 30 Afghans were at the base when the latest attack occurred.
"I stress that there is no simple one-line explanation to this incident or the previous incident.
"We need to do some digging, further digging," he added when asked whether he knew of the motive. "It could be personal grievance, it could be religious ideology. We don`t know, there was no indication."
It was the third such shooting to affect Australian troops this year, after an Afghan soldier killed an Australian lance corporal in May as they shared guard duties at a patrol base in the Chora Valley.
The latest incident took place just days after Australian Prime Minister Julia Gillard visited Afghanistan, making an unannounced stopover to meet troops in the restive southern province of Uruzgan.
She said Wednesday that Australians would continue to train Afghan National Army soldiers, despite the risk.
"I`m very conscious that this attack, coming so soon after the dreadful attacks of October 29, will... cause Australians to question our mission in Afghanistan and the trust we have in Afghan National Army soldiers," she said.
"As distressing as these incidents are, as dreadful as these incidents are, our mission in Afghanistan does need to continue.
"Training is pivotal to that mission and our purpose in Afghanistan is to deny Afghanistan as a country in which terrorists can train to wreak violence around the world," she added to reporters.
Australia has 1,550 troops stationed in the strife-torn country, with 32 so far killed in the conflict.
The country`s troops were first deployed to Afghanistan in late 2001 before being pulled out in 2002. They were redeployed in 2005 and have been training Afghan soldiers in Uruzgan.
Canberra intends to keep troops in the central Asian nation until 2014.
AFP/H-RN
Editor: Jafar M Sidik
Copyright © ANTARA 2011
