Thirty US troops including special forces died when the Taliban shot down their helicopter, officials said, in the biggest single loss for foreign troops in the decade-long war.
Seven Afghan special forces and an interpreter were also among the dead late Friday when a rocket fired by Taliban rebels hit their Chinook as it began to take off after a firefight in Wardak province, southwest of the capital Kabul.
The crash followed a night raid that a witness said targeted a Taliban commander's home -- a key strategy by US-led forces as they seek to end the war, but one repeatedly criticised by the Afghan president for causing civilian deaths.
|A US soldier from the 3rd Platoon, Charlie Company, 2-87 Infantry, 3d Brigade Combat Team greets Afghan villagers as troops seal a canal running thru Highway 1 in the outskirts of Kandalay village in Kandahar province on August 6, 2011|
US President Barack Obama paid tribute to those who died and said the incident was a reminder of the "extraordinary sacrifices" made by the men and women of the military and their families.
Defence Secretary Leon Panetta vowed the US would "stay the course" in Afghanistan despite the latest loss. All foreign combat forces are due to leave by the end of 2014, but intense violence in recent months has raised questions over the prospects for Afghan forces as they take over.
The Taliban claimed responsibility for the attack and local and Afghan army authorities said an insurgent rocket had brought the chopper down.
The NATO-led International Security Assistance Force (ISAF) said 30 of its troops, one civilian interpreter and seven Afghan commandos were killed. All the ISAF service members were from the US, it said.
Afghan President Hamid Karzai offered condolences over the US deaths.
"The president of the Islamic Republic of Afghanistan expresses his sympathy and deep condolences to US President Barack Obama and the families of the victims," a statement from his office said.
US television networks reported that 25 of the dead in Friday's attack were US Navy SEALs. Sources in the Obama administration told AFP that the victims came from the army, navy and air force, without saying if they were SEALs.
Contrary to several US media reports, the dead were not part of the special forces team that killed Al-Qaeda leader Osama bin Laden in a raid in Pakistan in May, the sources said.
The incident is the deadliest for foreign troops in Afghanistan since American and other international forces ousted the insurgents from power in 2001 in the wake of the September 11 attacks.
The previous biggest death toll saw 16 American soldiers killed in 2005 when a Taliban rocket hit their Chinook in the eastern province of Kunar.
One man who said he witnessed Friday's crash, Mohammad Saber, told AFP that the helicopter came down during a late-night operation in his village.
"At around 10:00 pm last night (1730 GMT), we heard helicopters flying over us," he said. "We saw one of the helicopters land on the roof of a house of a Taliban commander, then shooting started.
"The helicopter later took off but soon after taking off it went down and crashed. There were other helicopters flying as well."
Wardak provincial spokesman Shahidullah Shahid said a rocket fired by insurgents "completely destroyed" the Chinook as it was taking off.
The Afghan army commander for the region, General Abdul Razeq, also said the helicopter was "shot down by a rocket fired by the enemy".
Chinooks are widely used by coalition forces in Afghanistan for transporting large numbers of troops and supplies around the war zone.
The defence ministry in Kabul said the seven local troops who died were members of Afghanistan's special forces.
Taliban spokesman Zabiullah Mujahid claimed the group was responsible for shooting down the Chinook and acknowledged that eight insurgents had been killed.
There are currently around 140,000 foreign soldiers in Afghanistan, around 100,000 of them from the US, but all combat forces are due to leave by the end of 2014.
Some troop withdrawals have already begun as part of a transition that has already seen Afghan security forces take control of key regions this summer.
A total of 342 foreign troops -- 279 from the United States -- have now been killed in Afghanistan this year, according to an AFP tally based on the independent website iCasualties.org.
Foreign troop commanders say the focus of the war is likely to shift to the east of the country, close to Pakistan where insurgents have hideouts, in the coming months