US troops and Afghan police accidentally fought a four-hour pitched battle against each other yesterday in the latest accident involving Western forces in Afghanistan.

US Marine Special Forces operating with Afghan troops in Farah province, near the Iranian border, were involved in the nighttime firefight with local police, nine of whom were killed when the Americans called in air support.Younus Rasuli, deputy governor of the province, said the police had had no warning that US and Afghan forces were in their area.

The US military said that its forces, along with Afghan troops, had retaliated after being attacked by “a nonuniformed hostile force”. It added: “The combined patrol signalled their status as coalition forces but continued to receive fire.”

Yesterday Nato apologised after two mortar rounds fired from a US base fell half a mile short of their target and killed four civilians.

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