A British soldier has been killed in a militant attack in the south of Afghanistan, raising the death toll for British forces in the Afghan war to at least thirty in 2011. The British Defense Ministry announced that the marine was seriously injured after a grenade was thrown into his checkpoint in the Nad-e Ali district of Afghanistan's Helmand province and died in hospital at Camp Bastion, Britain's main base in the province. "The Royal Marine was part of a foot patrol deployed to reassure local residents, and deter and disrupt insurgent activity, when they came under small arms attack," Task Force Helmand spokesman Major Rolf Kurth said. "With the help of mortars and close air support, they broke contact with the insurgents and returned to their checkpoint," he added. The militants further carried out an assault on the checkpoint which killed the Briton, the spokesman went on to say. Friday's death takes the total number of British military casualties in Afghanistan since the US-led invasion of the Asian country in 2001 to 378, the report said. Britain has almost 9,500 soldiers in Afghanistan that are stationed in central Helmand and involved in fighting militants and training local security forces.