US Marines and Afghan troops were bogged down by sniper fire and home-made bombs on the third day of their biggest offensive since the overthrow of the Taleban in 2001.

Nato and allied forces were meeting fierce resistance in their battle to seize the Taleban’s main stronghold in southern Afghanistan, and were able to advance only 500 yards yesterday.

Multiple firefights broke out in various areas in and around Marjah, the Taleban’s most important opium-growing centre in Helmand, the country’s most violent province.