Australia has suffered its worst day in conflict since the Vietnam War after five soldiers were killed in two separate incidents in Afghanistan.
Prime Minister Julia Gillard has left the Pacific Islands Forum in Rarotonga to return to Australia. Speaking to reporters before her departure, she said it was the worst loss of Australian lives in combat in decades.
"This is a very big toll, but this means that in a war of so many losses this is our single worst day in Afghanistan. I believe this is the most losses in combat since the days of the Vietnam War and the Battle of Long Tan."
The Defence Force confirmed three soldiers were killed by a man in an Afghan army uniform in "a green on blue" attack at a base in Uruzgan Province in the south of the country on Wednesday.
Two other Australian soldiers were wounded in that incident. One suffered serious gunshot wounds and has been evacuated for further treatment, while the other has minor wounds and remains at the patrol base.
In the second incident, two special forces soldiers were killed when their helicopter crashed in the Helmand province early on Thursday, the ABC reports.
Acting Defence Force Chief Air Marshall Mark Binskin said the soldiers' families have all been notified, but they have asked for personal details not to be released at this time.
Air Marshall Binskin did say all three killed in the first incident were based at the Gallipoli Barracks in Brisbane.
One was a 40-year-old who had previously served in Iraq. The second was a 23-year-old private and the third was a 21-year-old sapper - both were on their first operational deployment.
Air Marshall Binskin says a crewman from the International Security Assistance Force (ISAF) was wounded in the helicopter crash and an investigation is under way.
Thirty-eight Australian soldiers have now died in Afghanistan since 2002. Most troops are based in the Uruzgan region.
Third 'green on blue' fatal attack
NATO has struggled to counter the so-called "green on blue" attacks in which uniformed Afghans turn their weapons against international allies.
The assaults have spiked this year, with more than 30 attacks claiming the lives of 45 coalition troops, comprising about 14% of the overall death toll in the war for 2012, according to ISAF.
Wednesday's incident is the third in which Australian soldiers have been shot and killed by Afghan soldiers in this type of attack, AAP reports.
In May last year, an Afghan soldier shot and killed Lance Corporal Andrew Jones at a patrol base in the Chorah Valley. The culprit fled, but was subsequently located by United States forces and shot dead.
In October last year, another Afghan soldier opened fire on Australian and Afghan troops at a patrol base in Kandahar Province, killing three Australian soldiers. The Afghan soldier was immediately shot dead.
In a third incident, in November, an Afghan soldier shot and wounded three Australians. He escaped and remains on the run.