The Australian military has suffered its darkest day in combat since the Vietnam War, with five Diggers killed in two separate incidents in Afghanistan.
In a blow to the Australian mission to the war-torn nation, three soldiers died after an Afghan soldier began shooting at a patrol in Oruzgan province about twilight on Wednesday.
Then early yesterday, two Australian commandos were killed in a helicopter crash during a night raid in Helmand province.
The deaths bring the number of Australian soldiers killed in Afghanistan to 38.
Acting chief of Defence, Air Marshal Mark Binskin, said the attack on the Australian soldiers, aged 21, 23 and 40, was at patrol base Wahab in the Baluchi Valley, about 20km north of the main Australian base of Tarin Kowt.
The Afghan soldier, believed to be a relatively new recruit, approached them while they were resting and fired a sustained burst of automatic fire at close range, killing three Diggers and wounding two.
Australian soldiers returned fire but the attacker escaped over a wall and into a village.
Coalition forces were hunting the Afghan and hoped to take him alive.
The soldiers killed were part of an Australian military mentoring team who travel from base to base training the Afghan army.
The names of the three dead Diggers have not been released but they were all based at Brisbane's Enoggera Barracks.
The incident is the fourth time an Afghan soldier has turned on Australian forces, resulting in the deaths of seven Diggers.
Such incidents are known within Defence as green on blue attacks, referring to colours signalling threat levels - blue is friend, green is ally and red is enemy.
There have been more than 30 such attacks on coalition troops this year.
The Taliban is often quick to claim responsibility for planning such attacks but they are more often the result of cultural clashes between Westerners and Afghans.
Air Marshal Binskin said security was already high at Australian bases but there would be another review to find out if further improvements could be made. He conceded the morale of Australian troops had "taken a hit" but said soldiers remained committed to the mission.
Air Marshal Binskin said Defence had some personal details of the perpetrator of the green on blue attack but no idea of his motives.
Prime Minister Julia Gillard cut short her visit to the Cook Islands to return to Canberra soon after news of the deaths broke.
She pledged Australia would not withdraw from the conflict early and would stick to the 2014 drawdown deadline.
"This is news so truly shocking that it's going to feel for many Australians like a physical blow," Ms Gillard said.
"But this is a war with a purpose and a war with an end."
New Zealand announced last week that it would accelerate its withdrawal from the conflict after three Kiwis were killed in the northern province of Bamiyan.
In yesterday's incident, the two commandos were killed while on a mission targeting an insurgent figure.
The US Black Hawk helicopter crashed in darkness as it was landing and rolled over. Though the cause of the crash is not known, it is not believed it was a result of enemy action.
The men who died, aged 23 and 30, were veterans of the decade-long Afghan war. They were from the 2nd Commando Regiment, based in Sydney.
Australia has about 1500 troops in Afghanistan with most based in Oruzgan province.
The Federal Government has committed to withdrawing the bulk of Australian forces by the end of 2014, though Australian special forces will likely stay in the country for a further three or four years.
NATO forces are currently handing over security to Afghan forces under a process dubbed "transition".
It is planned that local troops should have full responsibility for security by the end of 2014, with a small NATO force staying behind to give back-up in extreme circumstances.
The deaths of the Diggers on Wednesday and Thursday are the highest in a 24-hour period since five Australian soldiers were killed in Australia's last major firefight in Vietnam on September 21, 1971.The Afghan Government said last week that it would review the files of all personnel in a bid to curb green on blue attacks.