Taliban say they downed helicopter in the deadliest single combat incident of the decade-long war.
A NATO helicopter has crashed in eastern Afghanistan during a battle with the Taliban, killing 30 US and seven Afghan soldiers and one civilian interpreter, a statement from the Nato-led coalition has said.
The statement on Saturday said a Chinook helicopter had crashed in Syedabad in central Maidan Wardak province, west of capital Kabul, and identified the Americans as special forces troops.
More than 20 US navy SEALs from the broader unit that killed Osama bin Laden were among those killed in the crash, though none of the victims were involved in that raid, the New York Times reported.
The troops from SEAL Team Six were flown by a crew of the 160th Special Operations Aviation Regiment, according to one current and one former US official. Both spoke on condition of anonymity because families are still being notified.
One source said the team was thought to include 22 SEALs, three air force air controllers, seven Afghan army troops, a dog and his handler, and a civilian interpreter, plus the helicopter crew.
The Taliban quickly claimed to have shot down the helicopter during a firefight. They also said eight of their fighters were killed in the fighting.
"They wanted to attack our mujahideen who were in a house, but our mujahideen resisted and destroyed a helicopter with a RPG (rocket-propelled grenade) rocket," Taliban spokesman Zabihullah Mujahid said by telephone from an undisclosed location.
However, sources on the ground told Al Jazeera "that the helicopter was apparently taking off from a roof of a building during this operation when it then crashed,"
"It is looking like it is going to be one of the single largest losses of life for coalition forces in Afghanistan in the last 10 years," said Bernard Smith, our correspondent in Kabul.
"The joint forces [foreign and Afghan] conducted an operation against the Taliban in Syedabad district last night," said Shahidullah Shahid, the provincial spokesman.
"Eight insurgents were killed. A coalition helicopter that was firing on insurgents at the time crashed.
"We're not sure if this happened due to insurgent fire or not but there were some casualties of foreign troops due to the crash."
Shahid said coalition and Afghan officials were investigating the crash site of the aircraft, a twin-rotor Chinook helicopter, on Saturday.
A spokesman for the NATO-led International Security Assistance Force (ISAF) in Afghanistan said they were currently assessing what had happened.
Aircraft crashes are relatively frequent in Afghanistan, where insecurity and difficult terrain make air travel essential for coalition forces transporting troops and equipment.
In June 2005, 16 US troops were killed when their helicopter crashed in eastern Kunar province after apparently being hit by arocket-propelled grenade.
There have been at least 17 coalition and Afghan aircraft crashes in Afghanistan this year.
Elsewhere, in the Nad Ali district in southern Afghanistan's Helmand province, up to eight civilians were killed in a NATO airstrike on Friday, governor Shadi Khan said.
"A group of Taliban attacked a foot patrol of NATO forces," Khan said.
"Subsequently, an air strike targeted the house of an imam of a mosque in the area. As a result the imam, his wife and six of their children were killed."
Daud Ahmadi, the Helmand provincial spokesman, said he was "aware that there have been some civilian casualties as a result of a NATO air strike in Nad Ali district" and that an official delegation had been dispatched to investigate.
The incident appears to be the latest in which Afghan civilians have been accidentally killed by NATO military operations.
It comes as the Afghan army and police ready themselves to take full charge of the country's security as NATO starts withdrawing its forces this year.