Four Australians were killed and 10 wounded in three earlier, separate green on blue attacks, named for the US colour coding system that designates Afghan soldiers as green and international forces as blue.
Prime Minister Julia Gillard yesterday cancelled a meeting with Cook Island Prime Minister Henry Puna at the Pacific Islands Forum to be briefed on the losses and later said green on blue attacks were "corrosive of trust" between Australian and Afghan forces. She headed home to Australia.
About 1500 Diggers are based in Afghanistan, with most involved in training the Afghan National Army's 4th Brigade in Uruzgun province.
In April Gillard announced that most of the troops would return home within 12 to 18 months, well ahead of the earlier December 2014 deadline. Special forces units are expected to remain.
Yesterday she said that while Afghanistan was a war "with a purpose and ... with an end", many Australians would question why their troops remained there.
"We went for the right reasons in our national interest to prevent Afghanistan from being a safe haven for terrorists who would come and kill Australians and so many innocent civilians ..." she said.
"This news is so shocking that it will feel for many Australians like a physical blow ...
"It is hard to imagine what the families of these five men are feeling. Their loss is immense, their grief will be sharp ...
"Our hearts go out to those in the field and to the people who are endeavouring to hunt down the Afghan who has killed our Australians, and to those investigating the helicopter crash."
Opposition Leader Tony Abbott said the deaths were a black day for the Defence Force, and Governor-General Quentin Bryce said it was one of Australia's darkest days, but that the terrible losses "will only steel the resolve of those who continue this important work".
Chief of Defence Air Marshal Mark Binskin said the soldiers had been relaxing at the end of the day when they were shot.
The special forces soldiers died when a helicopter apparently rolled after landing in Helmund province.
The number of green on blue attacks has accelerated, with almost 50 Coalition troops killed so far this year. Casualties from the attacks have risen from 6 per cent of the total last year to 14 per cent.
Taleban leader Mullah Omar said this month his fighters had infiltrated Coalition units under a plan formulated last year.
DEADLY INCIDENTSTHE CASUALTIES
* Three died when an individual wearing an Afghan National Army uniform opened fire with an automatic weapon from close range.
* Two other soldiers were wounded in the same incident inside a patrol base 20km north of Tarin Kowt.
* Two special forces soldiers were killed, and an ISAF crew member wounded, in a separate incident while travelling in a helicopter that crashed in Helmand province.
GREEN ON BLUE ATTACKS
* They involve Afghan soldiers turning on their international allies.
* Taleban infiltration accounts for about a quarter of the incidents.
* More than 45 coalition troops have now been killed in about 30 "green on blue" attacks.
* These attacks have made up about 14 per cent of the overall death toll in the war for this year.
* Seven Australian soldiers have been killed in three separate incidents in green on blue attacks.
- AAP
