A British marine has died of injuries sustained in Afghanistan, the Ministry of Defence said Monday, taking the country's total military death toll in the conflict to 300. The grim landmark comes during a year which has already seen the second-highest number of British fatalities since operations began in 2001 -- 55. "It is desperately sad news. Another family with such grief and pain and loss. Of course the 300th death is no more or less tragic than the 299 that came before," said Prime Minister David Cameron. "But it is a moment, I think, for the whole country to reflect on the incredible service and sacrifice and dedication that our armed services give on our behalf." He added that British troops would leave Afghanistan "as soon as they (Afghans) are able to take care and take security for their own country". The latest victim, from 40 Commando Royal Marines, died in hospital in Birmingham, central England, Sunday after being seriously injured in an explosion in Sangin, Helmand Province, on June 12, it said. Britain has around 9,500 troops in Afghanistan, making it the second largest contributor to the NATO-led International Security Assistance Force. They are based in the troubled southern Helmand province, battling Taliban insurgents and training local security forces. Following news of the 300th fatality, Defence Secretary Liam Fox stressed that he hoped to "bring our forces home" from Afghanistan once Afghans can provide sufficient security and governance for themselves. "The last nine years have seen British forces at the forefront of the campaign, for the last five working hard in one of the most challenging areas of the country building Afghan capacity to secure and govern their own country -- a process which ultimately will allow us to bring our forces home". Cameron added: "We are paying a high price for keeping our country safe, for making our world a safer place, and we should keep asking why we are there and how long we must be there. "The truth is that we are there because the Afghans are not yet ready to keep their own country safe and to keep terrorists and terrorist training camps out of their country. That's why we have to be there. "But as soon as they are able to take care and take security for their own country, that is when we can leave." The death toll in Afghanistan has risen steadily since 2006 and the number of fatalities surged in 2009, when 108 troops died. The death toll reached 200 on August 15 last year. The spike followed the launch of Operation Panther's Claw in the build-up to Afghanistan's presidential elections. As the operation tried to shift from front-line fighting towards training local Afghan forces, the death toll did not slow up as new threats emerged. Cameron's Conservative-Liberal Democrat coalition government, which took office in May, has made Afghanistan its top foreign policy priority. Cameron visited Afghanistan on June 10-11, holding talks in Kabul with Afghan President Hamid Karzai and visiting troops at their main Camp Bastion base in Helmand. He ruled out increasing Britain's troop commitment and called for quicker progress to bring troops home. Cameron warned last week that Britain "must be ready for further casualties over the summer months" and described 2010 as "the vital one" for overcoming the Taliban. The name of the dead marine has not yet been released although his family have been informed of his death. Of the 300 British personnel who have died in Afghanistan, 266 were killed as a result of hostile action.