About 3,000 troops are involved in Operation Silicon

Major-General Jacko Page replaces his Dutch predecessor as head of operations in Helmand and neighbouring areas.

It comes as about 3,000 UK, Danish and Afghan troops continue to push through the lower Sangin Valley, a known insurgent stronghold in the south.

Operation Silicon aims to drive Taleban fighters out of the opium-producing area and bring security to Afghanistan.

The fighting's not over either - the Taleban will no doubt be fighting for every inch of ground Valley battle against Taleban 'Civilians dead' in assault

BBC correspondent Alastair Leithead, who is embedded with the British forces, said the Ministry of Defence had not commented on reports that more 40 Taleban were killed.

Nato troops saw heavy fighting lasting between six and seven hours, the BBC's correspondent said.

At one point, British infantry from the First Royal Anglians were fighting a determined Taleban defence on three fronts.

Engineers are now working to set up bases around the town of Gereshk in the hope the Afghan army can take control of defence in future.

The Sangin Valley mission, which involves about 3,000 personnel, forms part of Operation Achilles - described as Nato's largest offensive against the Taleban in the south.

It involves more than 4,500 Nato troops, from the UK the US, Estonia, Denmark, Netherlands and Canada and nearly 1,000 Afghan soldiers.

Lt Col Mike Smith, Nato's regional command-south spokesman said an ammunition cache and other equipment were seized during Monday's operation.

"This phase of Operation Achilles is a significant step towards establishing the security conditions necessary to enable key reconstruction and development projects in the area," he said.