Helicopter gunships and troops blasted a valley in southern Afghanistan yesterday in a huge offensive by Nato and local forces against Taliban insurgents, many of whom broke out of jail last week.

The defence ministry in Kabul said dozens of Taliban, including foreign militants, were killed in a Nato air strike and two Afghan army officers also died in the operation, in Arghandab district outside Kandahar city.

The ministry said three Taliban group leaders were killed further south, adding 12 other insurgents died in another encounter with the army in neighbouring Zabul.

Some 600 Taliban fighters on Monday took over villages in Arghandab, days after freeing hundreds of inmates in an attack on Kandahar city's main jail, according to the Taliban and an Afghan official.

Yesterday, four Afghan police were killed when a remote controlled bomb hit their vehicle in the southeastern province of Khost, a provincial official said. In neighbouring Paktika, two soldiers from the Nato-led force were killed and 10 wounded by a separate blast, the alliance said.

On Tuesday, four British soldiers from the Nato-led force were killed after a roadside bomb struck their vehicle in Helmand, bordering Kandahar, the bloodiest single incident in one day against the British soldiers in Afghanistan.