Earlier Thursday, the International Security Assistance Force (ISAF) said three soldiers in the Nato-led force in Afghanistan had been killed by a member of the Afghan security forces.
The attack occurred in the restive southern Uruzgan province where about 1,500 Australian troops are deployed.
"Defence is currently in the process of informing the next of kin of the ADF personnel involved," the ADF said in a statement.
ISAF said the latest killings were an "insider attack" - a trend that has caused growing dismay among coalition commanders.
"An individual wearing an Afghan National Army uniform turned his weapon against International Security Assistance Force service members in southern Afghanistan yesterday, killing three," ISAF said in a statement.
"The incident is currently under investigation."
Nato has struggled to counter the so-called "green-on-blue" attacks in which uniformed Afghans turn their weapons against their international allies.
The assaults have spiked this year, with more than 30 attacks claiming the lives of 45 coalition troops, comprising about 14 percent of the overall death toll in the war for 2012, according to ISAF.
The latest deaths are the third incident in which Australian soldiers have been shot and killed by rogue Afghans in "green-on-blue" attacks.
In May last year, an Afghan soldier shot and killed an Australian with whom he was sharing guard duties at a patrol base in the Chora Valley. The culprit fled but was subsequently located by US forces and shot dead.
Then in October last year, another Afghan soldier opened fire on Australian and Afghan troops during a parade at a patrol base in Kandahar province, killing three Australians and wounding seven others.
The Afghan soldier was shot dead.
In another incident in November, an Afghan soldier shot and wounded three Australians. He escaped and remains on the run.
A close ally of the United States, Australia's Afghan deployment began in 2001 before Canberra pulled out, only to redeploy to the arena in 2005.
Australia announced earlier this year that it would begin withdrawing its forces in 2013, quicker than planned due to significant security gains and as Canberra has faced increased pressure over the long-running Afghan campaign.
Source: agencies
