Image copyright AFP Image caption Afghan police are taking on greater responsibility for security ahead of Nato's withdrawal

At least 10 Afghan security personnel have been killed in a gun battle with Taliban insurgents in the western province of Herat, officials said.

Five policemen, including the chief of Aubi district, and five soldiers died after Taliban fighters attacked a convoy, local officials said.

Two Taliban leaders also died and 25 others were arrested, officials added.

Afghan police and troops are playing an increasing role in national security as Nato troops prepare to leave in 2014.

The attack took place in the Genewa area between Aubi and Chesht Sharif districts late on Monday, a spokesman for the provincial governor's office told the Afghan Islamic Press (AIP).

A spokesman for the provincial governor, Muhiudin Noori, said the Afghan troops had been looking for a group of insurgents who had earlier set up a roadblock, stopping and seizing passing vehicles, when they were ambushed, AP reports.

The Taliban has so far not commented.

Correspondents say casualties among Afghan security forces are rising as they take over during the transition process.

Herat has experienced sporadic outbreaks of violence although militant attacks have been concentrated mainly in the south and east of Afghanistan.

Nato handed security control of the city of Herat to Afghan forces in July 2011.