Three Australian soldiers have been killed and seven injured in a helicopter crash in the rugged north of Kandahar Province in Afghanistan.
It is believed at this point that the helicopter was not shot down by enemy fire but it is unknown what caused the crash, Defence Force Air Chief Marshal Angus Houston.
"This was not the result of enemy action," Air Chief Marshal Houston said.
Other Coalition helicopters were able to land nearby the crash site and recover the bodies and wounded soldiers.
Of the seven wounded soldiers, two are in a serious condition and have been airlifted to a US Air Force base at Bagram.
The dead soldiers were members of the 2nd commando regiment and had done three tours of Afghanistan.
Air Chief Marshal Houston said the commandoes were last week were involved in a major battle in the same region in which the helicopter crashed.
"We don’t know what caused the crash yet but the terrain is rugged, the helicopters are often heavily loaded, it’s at high altitude and it was three o’clock in the morning. All of these factors will no doubt be considered," he said.
Air Chief Marshal Houston said the soldiers were highly experienced.
"Time after time, they have taken the fight to the enemy with courage and determination," he said.
"I have nothing but admiration and respect for these very brave and committed Australians."
Prime Minister Kevin Rudd said it was a "tragic day for Australia and the Australian Defence Force".
"This is a very heavy price to pay," he said.
But he said Australia’s mission in Afghanistan was critical, Mr Rudd said.
"We work beside our allies ... to avoid Afghanistan once again becoming a breeding ground for terrorists who can then strike at innocent Australians both at home and abroad."
Mr Rudd said all Australians owed the soldiers a debt of gratitude for their service and sacrifice.
"It will never be forgotten," Mr Rudd said.
The Prime Minister said his thoughts were also with the seven soldiers who have been injured, promising that they would receive the best possible medical care.
Air Chief Marshal Houston sent a message of support to members of the Special Operations Task Group.
"I am immensely proud of your efforts, and I greatly respect what you’ve been able to achieve," he said.
"I ask you now to be there for each other, draw strength from all that you have accomplished, and use the support that we are offering as you deal with the loss of your close mates."
The crash brings Australia's death toll in Afghanistan to 16.
Another ISAF soldier - from another country - was also killed, Defence Minister John Faulkner said.
Standing alongside Air Chief Marshal Houston, Senator Faulkner said that he intended making a statement to Parliament about the timeframe for Australia’s mission in Afghanistan before the end of this week.
"Our nation today lost three courageous soldiers," Senator Faulkner said.
"This is a tragic day for Australia."
Air Chief Marshal Houston expressed condolences to the soldiers' families.
"On behalf of all the men and women of the ADF I extend my sympathies to the families of these three fine commandos we lost this morning," he said.
"We in the ADF are doing everything we can to support them at this time. But obviously they are very shocked and very distressed."
Australia suffered multiple casualties in Afghanistan this month.
Sapper Darren Smith, a 26-year-old combat engineer died in a roadside bomb blast.
The blast also killed Sapper Jacob Moerland, 21, and Sapper Smith's bomb detector dog, Herbie.
Today's crash comes as an Essential Research poll shows that public opposition to Australia’s involvement in Afghanistan has jumped by 11% since March last year.
With AAP
Statements did not identify the type of helicopter.  This file photo shows an S-70A-9 Black Hawk that Diggers use for tactical transport. 
Less than two weeks after two Australian soldiers () died in the explosion of a roadside bomb, three more Diggers and a US soldier were killed early yesterday morning in a helicopter crash in southern Afghanistan, while seven other soldiers are being treated for injuries.

 Angus Houston said in a statement this afternoon that two of the crash survivors are in a serious condition and will be moved with the other survivors to the US military hospital in .

The crash occurred at 03:39 yesterday local time (23:09 on Sunday, ) in the north of . Although the cause is still unknown, Houston said "the terrain is rugged, the helicopters are often heavily loaded, it’s at high altitude and it was three o’clock in the morning. All of these factors will no doubt be considered". Houston confirmed that enemy fire was not to blame for the crash.

These new casualties in the Afghan War brings Australia's death toll to sixteen, while that of the US comes to 1128 since the war began in 2001.

Despite this, Prime Minister Kevin Rudd, remains firm on the issue: "We work beside our allies ... to avoid Afghanistan once again becoming a breeding ground for terrorists who can then strike at innocent Australians both at home and abroad" and continued by saying that all Australians owe the soldiers a debt of gratitude for making the ultimate sacrifice in the line of duty.

Although the names of the soldiers have yet to be released, the tragedy follows last week's casualties where Australian combat engineers Darren Smith, age 26, and Jacob Moerland, age 21, were killed along side their bomb sniffer dog, Herbie in a roadside blast.