KABUL, Aug 7: Nato tried to confirm on Sunday if the Taliban had shot down a helicopter in Afghanistan, killing 38 in the largest loss of life suffered by foreign forces in a single incident in 10 years of war.

Thirty US soldiers — some from the Navy’s Seal Team 6, the unit that killed Al Qaeda leader Osama bin Laden — seven Afghans and an interpreter died in Friday night’s crash, just two weeks after foreign troops began a security handover to Afghan forces.

The Taliban claimed responsibility for bringing down the helicopter with a rocket-propelled grenade. A US official in Washington said the helicopter was believed to have been shot down.

Nato-led Isaf 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 site in a valley about 80km southwest of the capital was still ongoing.

The deadly crash comes at a time of growing unease in the United States and Europe about the increasingly unpopular and costly war. The last foreign combat troops are due to leave Afghanistan by the end of 2014 but some US lawmakers are asking whether that timetable is fast enough.

The CH-47 Chinook crashed in central Maidan Wardak province in a hard-to-reach valley surrounded by rugged mountains.

Despite its proximity to Kabul, 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.

A US official said some of the dead Americans were members of Seal Team 6, but none of them had been part of the Bin Laden raid in Pakistan in May.

The devastating death toll will likely raise more questions about the security transition and how much longer troops should stay.

“While acknowledging the immense personal tragedy of the loss of life in this helicopter disaster it is even more important to acknowledge that a greater tragedy would be to buckle under an understandable wave of emotion, and use it as a reason to withdraw now,” Gen Richard Dannatt, British army commander from 2006 to 2009, wrote in the Sunday Telegraph.

With doubts lingering about the cause of the crash, Mr Karzai met his security advisers on Sunday to discuss what he called the “helicopter incident”. He warned them to be on guard for more attempts by militants to derail the transition process.

“As there is the transition process going on enemies of Afghanistan want to disrupt the national process by any means,” Mr Karzai said in a statement released by the presidential palace.

US and other Nato commanders have claimed success in reversing a growing militancy in the Taliban’s southern heartland, although insurgents have demonstrated an ability to adapt their tactics and mount attacks in other areas.

But violence is at its worst in Afghanistan since the start of the war, with high levels of foreign troop deaths and record civilian casualties during the first six months of 2011.

Last year was the deadliest of the war for foreign troops in Afghanistan with 711 killed. The crash in Maidan Wardak and Sunday’s deaths took the toll of foreign troops killed so far in 2011 to at least 383. More than two-thirds were American. —Reuters