Australia suffered its worst combat losses since the Vietnam War when five troops were killed in Afghanistan, officials said on Thursday, Aug 30, prompting Prime Minister Julia Gillard to return home early from a regional Pacific leaders' conference.

According to Reuters, officials from the Australian Defense Force and the NATO-led coalition said three Australians had been killed in southern Afghanistan on Wednesday by an Afghan wearing a soldier's uniform, bringing to 45 the number of NATO-led coalition troops killed in rogue shootings this year.

Australian officials later announced another two troops had died in a helicopter crash in the south on Thursday.

"This is news so truly shocking that it's going to feel for many Australians like a physical blow," an emotional Gillard told reporters in the Cook Islands, where she was attending a forum of Pacific islands leaders.

Gillard said she would cut short her visit and return to Australia later on Thursday for briefings on the deaths.