British Prime Minister Gordon Brown is in Afghanistan and has visited UK troops near the front lines with the Taliban in the country's volatile south. Brown says the presence of international troops in Afghanistan is critical to stem terrorism and to support Afghan elections next year. Brown is visiting one day after four troops were killed Helmand. He says there is "disgust and horror" that the Taliban used a 13-year-old boy as a suicide bomber in one of the attacks, which killed three Marines. The prime minister says people in Britain and elsewhere are safer because of the international effort in Afghanistan to fight the Taliban. Britain has some 8,200 troops in Afghanistan, based mostly in Helmand.