The US military has admitted shooting dead three of its Afghan allies and wounding two others in a bungled operation in the troubled east Afghan province of Paktia.

Special forces opened fire during a night-time raid on a compound after believing themselves in danger, said Lieutenant Frank Merriman, a spokesman for US Central Command.

One soldier had seen an unidentified fighter point a rocket-propelled grenade in his unit's direction and his commander gave the order to fire, the spokesman said.

A BBC correspondent in Kabul says the episode is an embarrassment to the US in a sensitive region of Afghanistan and underlines the complexity of military operations there.

"The firefight, which lasted just a few moments, resulted in the deaths of three and the wounding of two," said Lieutenant Merriman.

According to the US military, a combined force of more than 100 US special forces and Afghan troops were approaching a walled compound in the village of Khomar Kalay, near the provincial capital Gardez, in the early hours of Friday.

As they searched the site for al-Qaeda and Taleban militants, they reportedly noticed several fighters taking up fighting positions inside.

At the same time, the military said, another group of 10 to 12 armed men came sprinting towards them in what appeared to be a flanking manoeuvre.

Following the shooting, the 17 remaining Afghan fighters surrendered and it turned out they were pro-government forces from a neighbouring province, Logar.

More precautions

A US spokesman in Afghanistan, Colonel Roger King, said he was concerned about the loss of allied lives.

The US has long been hunting militants in Paktia

"Efforts will be made to place co-ordination measures into effect to prevent similar occurrences in the future," he said.

Special forces have been working with allied Afghan forces to hunt for militants around Gardez and other areas near the Pakistan border.

But the area is also home to feuding warlords and armed fighters loyal to them.

The BBC's Ian McWilliam says this "friendly fire" incident is a deadly illustration of the difficulties of hunting remaining militants in this remote region.

A rebel warlord, Padsha Khan Zadran, has been fighting to dislodge the province's governor, compounding the difficulties.