A US civilian cargo plane has crashed at Bagram airbase in Afghanistan, killing its seven crew, officials say.

The plane came down shortly after take-off and crashed within the boundaries of the huge US-run airbase, said a Nato spokesperson at the base.

The Taliban claimed responsibility for the crash, but their involvement was denied by Nato.

Bagram, near the Afghan capital Kabul, is the largest military base for US troops in Afghanistan.

Witnesses said the plane reached an altitude of some 400m (1,300ft) before suddenly "falling out of the sky", Bagram's district governor, Abdul Shukor, told Reuters news agency.

The crash was confirmed by the plane's owners, National Air Cargo.

"We did lose all seven crew members," said a spokeswoman for the Florida-based firm.

The Taliban were quick to claim responsibility, telling the Pakistan-based Afghan Islam Press they shot down the plane.

But Nato's International Security Assistance Force (Isaf) said there were no reports of militant activity in or around the base at the time of the crash.

No cause for the crash has been given - Nato said it is being investigated.

The crash comes two days after four military personnel were killed in a crash in the southern Afghan province of Zabul, which officials said was also not due to military activity.