Six British soldiers believed killed in Afghanistan roadside bomb attack LASHKAR GAH, Afghanistan -- Six British soldiers were believed killed after an explosion hit their armored vehicle in southwestern Afghanistan, Britain's Ministry of Defense said Wednesday. If confirmed, it would be the biggest loss of life for British forces in the country since a plane crash in 2006. The soldiers were on patrol in Helmand province at the time of the blast on Tuesday evening. The military did not explain why they are unable to confirm whether the soldiers were killed. Confirmation of their deaths would take the overall tally of British forces killed in Afghanistan to 404 since the 2001 U.S.-led invasion to oust the Taliban. The soldiers, five from the 3rd Battalion the Yorkshire Regiment and one from the 1st Battalion The Duke of Lancaster's Regiment, were on a mounted patrol on Tuesday when their Warrior Armoured Fighting Vehicle was struck, the ministry said. In Helmand, a spokesman for the British Task Force said the families of the British soldiers have been informed. Qais Usyan / AFP - Getty Images More than a decade after the beginning of the war, Afghanistan faces external pressure to reform as well as ongoing internal conflicts. Sky News reported that it was the first time a British Warrior vehicle had been destroyed in Afghanistan. A second Warrior was reportedly traveling in a convoy with the one destroyed but it was not hit by the explosion, Sky said. "I utterly condemn those responsible for this incident who will ultimately fail to derail a mission that is protecting our national security at home and making real progress in Helmand Province," Britain's defense secretary Philip Hammond said in a statement. It is because of the continuing efforts of our armed forces ... that we are on course to build an Afghanistan that can stand on its own two feet when UK combat operations cease at the end of 2014. In London, British Prime Minister David Cameron said it was "a desperately sad day for our country." Britain reducing forces in Afghanistan Britain has some 9,500 soldiers in Afghanistan, a number due to be reduced in phases as it ends combat operations in the next two years. "I don't think soldiers see these round numbers, psychological milestones," said a senior British military source in Helmand, referring to the fact that the number of British deaths in the Afghan war had exceeded 400. It's disappointing to have this at the end of the tour but at this stage in the tour with how much progress we've made, we're able to contextualize this. Britain has lost more troops in Afghanistan than any other country except for the United States, which has counted at least 1,780 members deaths as a result of the U.S.-led invasion of Afghanistan in late 2001, according to an Associated Press count. The AP count of U.S. deaths is six fewer than the Defense Department's tally. At least 1,484 military service members have died in Afghanistan as a result of hostile action, according to the military's numbers. More than 2,800 troops from all nations have died since the start of the war on Oct. 7, 2001. There are about 130,000 troops from 50 countries serving with the international military coalition. The United States has been slowly drawing down its troops presence from a high of about 100,000 in 2011 to 68,000 at the end of summer. Britain has the largest contingent in the international force and says it will withdraw several hundred this year and almost all of them by the end of 2014. It is followed by Germany, with about 4,800, and France with 3,600 soldiers. The NATO-led international force in Afghanistan has been steadily handing over responsibility for security to the Afghan army and police. All foreign combat troops will have left Afghanistan at the end of 2014. Some troops may remain in a counterterrorism and training role after that date.