A spokesman for the Taliban said the group had shot down the helicopter, but American officials said there was no indication yet that enemy fire was the cause. The helicopter crashed in a Taliban-controlled area in the northern part of Kandahar Province known as Shah Wali Kot around 10 a.m. on Thursday, an official at the Kandahar provincial governor's office said.

American military officials declined to identify the type of unit to which the soldiers killed in the crash on Thursday had been assigned. However, a statement issued by the NATO command said three of them were part of United States Forces-Afghanistan, a command separate from the main NATO force that includes many Special Operations forces.

Maj. Martyn Crighton of the Army, a spokesman for the International Security Assistance Force Joint Command in Kabul, said it was not yet clear whether mechanical failure or Taliban fire was responsible.

"Currently, there is no operational reporting that indicates the helicopter was brought down by enemy fire," Major Crighton said. But he added that "it is far too early in the investigation to make any definitive statement about what caused the accident." He said everyone on board the helicopter was killed, and he confirmed that the crash occurred in Kandahar Province. But he declined to specify the precise location.

Jawed Faisal, a spokesman for the governor of Kandahar Province, said that the helicopter crashed in the Chinarto area of Shah Wali Kot. "It could be insurgents that shot it down, or it could be a technical problem," Mr. Faisal said, adding that no military operation was going on in the area at the time.

The Taliban had also claimed that its fighters in the Shah Wali Kot district had shot down a Chinook helicopter on Wednesday with a rocket-propelled grenade, killing 33 American soldiers who were flying overhead in support of a night raid on houses in the area, according to a translation of a Taliban statement by the SITE Intelligence Group.

Yet that statement was issued well before the time that both the Kandahar governor's spokesman and the American-led military command said the crash occurred, and Major Crighton denied that any NATO helicopter crashed on Wednesday.

Taliban insurgents continued their attacks on Afghan soldiers in the northern end of the country early on Thursday morning, detonating a roadside bomb a that killed two Afghan National Army soldiers and wounded three others in Baghlan Province. The soldiers had been riding in a pickup truck in the village of Ali Khwaja, according to Maj. Ghulam Hazrat, a spokesman for the Second Brigade of the Afghan National Army.

Jawad Sukhanyar and Sangar Rahimi contributed reporting.