Nato troops tried to ascertain on Sunday if Taliban insurgents had shot down a troop-carrying helicopter in Afghanistan, killing 38 people in the largest loss of life suffered by foreign troops in a single incident in 10 years of war.
In what has proved to be a bloody two days for foreign forces in Afghanistan, another two unidentified Nato troops were killed in two separate attacks by insurgents in Afghanistan's violent east and south, the coalition said.
Thirty US soldiers - some from the Navy's special forces SEAL Team 6, the unit that killed al Qaeda leader Osama bin Laden - seven Afghans and an interpreter died in Friday night's crash which came just two weeks after foreign troops began a security handover to Afghan forces.
The Taliban quickly claimed responsibility for bringing down the helicopter with a rocket-propelled grenade. Although it often exaggerates incidents involving foreign troops, a US official in Washington said the helicopter was believed to have been shot down.
The Nato-led International Security Assistance Force (ISAF) in Afghanistan confirmed the death toll overnight, which was first announced by Afghan President Hamid Karzai, and said the cause of the crash was still being investigated.
ISAF officials in Kabul remained tight-lipped on Sunday about possible causes of the crash and said the process of recovering the bodies from the crash site in a valley about 80 km south-west of the capital was still going on.
The deadly crash comes at a time of growing unease about the increasingly unpopular and costly war. Foreign forces are due to complete their security handover to Afghan troops and police by the end of 2014. The CH-47 Chinook crashed in central Maidan Wardak province in a hard-to-reach valley surrounded by rugged mountains.
Despite its proximity to the capital, the area is one of the most dangerous in central Afghanistan, with fighters from the Taliban, the al Qaeda-linked Haqqani network and other militant groups all active there.
"No words describe the sorrow we feel in the wake of this tragic loss," General John Allen, who took over from General David Petraeus three weeks ago as commander of all foreign troops in Afghanistan, said in a statement released overnight. "All of those killed in this operation were true heroes who had already given so much in the defence of freedom."
A US official said some of the dead Americans were members of SEAL Team 6. None of the dead had been part of the bin Laden raid in Pakistan in May.
The crash was the deadliest single incident for US troops in Afghanistan since the Taliban were toppled by US-backed Afghan forces in late 2001, ISAF said.
US Defense Secretary Leon Panetta said in a statement on Saturday that the United States would "stay the course" to complete the mission in Afghanistan, a sentiment echoed by Nato Secretary General Anders Fogh Rasmussen.
The crash will likely raise more questions about the security transition and how much longer troops should stay. All foreign combat troops are due to leave by the end of 2014, but some US lawmakers question whether that is fast enough.