A rocket fired by an unknown group on the US-run Bagram airbase in Afghanistan has destroyed a military helicopter on the eve of the anniversary of the September 11 attacks, killing three Afghans, officials say.

The Chinook helicopter caught fire and was destroyed as it prepared to take off late on Monday from Bagram air base, the largest US military base in the war-torn country, a NATO military spokesperson said on Tuesday.

"They were preparing for an operation," the spokesperson said, adding the helicopter was hit by "indirect fire".

Three Afghans were killed and several Afghan and foreign "service members" were wounded, the spokesperson said, but gave no further details.

Roshana Khalid, a spokeswoman for the Parwan province where the base is located confirmed the incident and said three Afghan intelligence agents were killed and two senior security officials wounded.

They were to conduct an anti-Taliban operation in an area near Bagram, she said.

"The helicopter was preparing to take off when a rocket fired by insurgents hit it. There were Afghan and [NATO] coalition personnel on board. Three Afghan intelligence personal were killed," Khalid said.

The wounded included the Parwan provincial operational chief of the intelligence agency and an army officer, Khalid added.

Bagram air base, about 50km north of capital Kabul is located in Parwan province which sees little of the Taliban-led insurgency, but the base comes under insurgent rocket attacks from time to time.

A similar attack on the base in August damaged the aircraft of General Martin Dempsey, chairman of the US Joint Chiefs of Staff who was visiting the war-torn country.

Two service members were wounded at that time.

Source: Agencies