Five Australian soldiers have been killed in what Prime Minister Julia Gillard calls the country's "single worst day in Afghanistan."
NATO officials say a person wearing an Afghan National Army uniform shot and killed three soldiers late Wednesday at a base in southern Afghanistan.
Afghan President Hamid Karzai said the incident took place in the Surkh Rez district of Uruzgan province and that two Australian soldiers were wounded in the attack.
It was the latest in a series of incidents in which Afghans in security force uniforms have turned their guns on coalition troops. At least 15 NATO soldiers, mostly Americans, have been killed in such attacks this month. More than 45 foreign troops have been killed in such attacks this year.
Two other Australian service members died early Thursday when their helicopter crashed in Helmand province. NATO said there was no enemy activity in the area at the time of the crash, and that both incidents are under investigation.
Gillard says Australia cannot let such deaths change its strategy, and that the country remains committed to completing its mission. Australia has more than 1,500 troops in Afghanistan. It announced earlier this year that its forces will withdraw from the country in mid-2013, a year earlier than previously planned.
The latest deaths bring the number of Australian troops killed in the Afghan war to 38.
NATO Secretary-General Anders Fogh Rasmussen tweeted Thursday, "our thoughts are with the loved ones of those killed and wounded in Afghanistan, and with the Australian people."
President Karzai said acts targeting foreign forces are designed to foster distrust between Afghan forces and their international partners. He noted in a statement that "there are foreign circles that have continually tried to impede Afghanistan from getting back on its feet [ from recovering]."
NATO says there are several factors behind the insider attacks, including personal grievances and arguments. The coalition attributes about 25 percent of such attacks to the Taliban.
Foreign combat troops are transferring security control to Afghan forces and are scheduled to be out of Afghanistan by the end of 2014.
Violence continues to hit Afghan civilians as well. Authorities say at least four people were killed Thursday in a mortar attack in the eastern province of Logar.
Some information for this report was provided by AP.