A bomb hit troops from the US-led coalition patrolling south of the Afghan capital Thursday, causing an unspecified number of casualties, the coalition said. In neighboring Pakistan, the government denied that its main spy agency was behind a recent assassination attempt on the Afghan president and took aim at Kabul for failing to prevent the attack. The bomb struck the coalition convoy on Thursday morning during a patrol in Wardak province, a coalition statement said. Troops secured the scene, but "the exact number and nature of casualties" was not immediately clear, it said. A freelance television cameraman filmed what he said was the aftermath of the Thursday attack. The footage showed the burning wreckage of a vehicle on a bend in a mountain road. Militants held up what looked like an M-16 rifle and dragged away a belt of ammunition. It was not possible to independently verify whether the footage was from the same incident reported by the coalition. The cameraman's name was withheld for his own security.