UK and other Nato troops are to launch an offensive to take back areas of southern Afghanistan, the British general in charge of forces there says.

Maj Gen Nick Carter said the operation would "assert the control" of the Afghan government in parts of Helmand now controlled by the Taliban.

He told BBC Radio 4's The World At One that Helmand was "a work in progress, with parts simply ungoverned".

There have been 251 UK service member deaths in Afghanistan since 2001.

Gen Carter said that if parts of Helmand were governed at all, "it's by parallel governments provided often by the Taliban".

He added: "If we're going to win the argument on behalf of the Afghan government... then we need to assert the government's control over those areas which are at the moment ungoverned."

'Ownership of responsibility'

The news comes as Nato's top commander in Afghanistan, US Gen Stanley McChrystal, said increased troop levels could bring a negotiated peace with the Taliban.

BBC News - Nato forces in Afghanistan to launch Helmand offensive