By Paul Anderson BBC correspondent in Kabul

An Afghan regional governor says at least eight civilians and two Taleban fighters were killed by American helicopter fire during an anti-Taleban operation in a remote area near the border with Pakistan.

A new US anti-Taleban offensive is under way

American military spokesmen say they cannot yet confirm the account.

According to the governor of Zabul province, Hafizullah Hasim, at least eight nomadic tribespeople were killed as they slept, when their tent was bombed by an American helicopter.

The target was two Taleban fighters, one a commander called Mullah Mohammed Gul Niazi. They had taken refuge in or near the tent.

The governor said the men were located in the Naubahar district, after a signal from a satellite phone they were using was intercepted.

Zabul and the neighbouring province of Uruzgan are at the centre of the latest American-led coalition campaign to hunt down regrouping Taleban fighters.

Operation Mountain Viper, launched at the end of August, has seen coalition troops confront hundreds of Taleban fighters - the largest grouping since the Taleban were driven from power nearly two years ago.

Around 150 fighters have been killed, along with several Americans and many more Afghan government forces.

If confirmed by American military spokesmen, the killing of the nomads recalls the worst incidents in Afghanistan of what the Americans call "friendly fire".

Last year 40 wedding party guests were killed in a helicopter attack launched in error.

Another eight people were killed by a bomb in a house in Paktika province several months ago. That was part of the ongoing hunt for al-Qaeda remnants.