All nine troops killed in the worst helicopter crash for the coalition in Afghanistan in four years were Americans, the Pentagon has confirmed .
It did not give any further information on why the aircraft carrying navy special forces went down.
Nato said there were no reports of enemy fire in a rugged area in the Daychopan district of Zabul province, where Tuesday's crash took place.
But Taliban spokesman Qari Yousef Ahmadi claimed that insurgents shot down the helicopter.
The Taliban often exaggerate their claims and sometimes take credit for accidents.
The US defence department released the identities of the troops on Wednesday evening, saying four were with the navy special forces - three of them Navy Seals - and the rest were soldiers.
The crash was the deadliest since May 2006, when a Chinook helicopter went down while attempting a night-time landing on a small mountain-top in eastern Kunar province, killing 10 US troops.
Aircraft are used extensively in Afghanistan by both Nato and the Afghan government forces to transport and supply troops because the terrain is mountainous and roads are few and primitive.
Lacking shoulder-fired missiles and other anti-aircraft weapons, the Taliban rely mostly on machine guns and rocket-propelled grenades to fire at aircraft during take-offs and landings.
Most helicopter crashes in the country have been accidents caused by maintenance problems or factors such as dust.