Nine Afghan police officers have been killed in air raids carried out by foreign coalition forces called in by mistake, the provincial authorities have said.

The raids in the western province of Farah came after police and soldiers mistook each other for Taliban fighters, Mohammad Younus Rasouli, deputy provincial governor, said.

The incident was sparked when police officers opened fire on soldiers from the Afghan National Army (ANA) and Nato's International Security Assistance Force (Isaf), he said.

"The ANA requested air support, and Isaf bombed the police post that killed nine police and injured five police," he said.

The police chief of Farah's Anar Dara district is in a serious condition after the raid, Rasouli said.

Ikramuddin Yawar, the police commander for western Afghanistan, said a team had been despatched to the area to investigate.

"Last night at around 1:30, a clash took place between ANA, ANP [Afghan National Police] and Isaf, each mistaking the other side as Taliban," Yawar said.

The Afghan defence ministry and Nato said they had no details on the incident, but were looking into the reports.

There have been several instances in Afghanistan where Afghan and Nato security forces have mistaken each other and launched deadly attacks. The forces have been accused of not properly co-ordinating their operations against Taliban loyalists, resulting in cases of mistaken identity.