The Taliban said they had downed the aircraft, although the militants have been quick to claim crashes caused by mechanical problems as successful hits.
"We hit the ISAF helicopter with a rocket-propelled grenade," said Qari Yousef Ahmadi, Taliban spokesman for the southern region.
The helicopter's landing was so hard it was destroyed, officials at the Pentagon told NBC news.
In Kabul, Nato said it was investigating the cause of the crash in Kandahar province, the birthplace of the Taliban.
The helicopter came down at about 11am in Shah Wali Kot, said Jawed Faisal, spokesman for the provincial governor. The crash site lies to the north-east of Kandahar city, an area with a strong insurgent presence.
Helicopter crashes have caused some of the highest death tolls of the war. Many have been the result of mechanical failures or errors by pilots flying in tough conditions, but insurgents have brought down some aircraft.
Last August, insurgents hit a Chinook with rocket-propelled grenades as it ferried troops on a combat mission, killing all 38 passengers on board.
The attack was the deadliest day of the decade-long war for the US military. Many of those killed were from Navy Seal Team 6, the unit that killed Osama bin Laden in a night-time raid deep inside Pakistan.
In January, a helicopter crash killed six soldiers, and on 12 March, Turkish soldiers and two Afghan girls were killed when a helicopter crashed into a house.
Asian Defence News