The key district of Sangin in the southern Afghan province of Helmand is once again on the verge of being overrun by the Taliban, BBC News reports citing an Afghan army commander.

The commander, who wishes to remain anonymous, told BBC that most of the district had already been taken.

He said the Afghan government now controls just a few square kilometres of Sangin city.

The Afghan army and local governor's office dismissed the claims.

A spokesman for the Helmand governor acknowledged there had been security problems in the past but said there was no "serious threat" that could lead to the fall of Sangin.

The unnamed commander warned that even the remaining areas under government control were under imminent threat.

Almost a quarter of British military personnel killed during the UK's combat mission in Afghanistan died defending Sangin.

There were reports in December last year that the district was almost entirely in Taliban hands but since then the Afghan government has sent in reinforcements.

Government officials have repeatedly asserted that, despite the continuing Taliban assault, Sangin is secure. The commander, however, paints a very different picture.