HERAT, Afghanistan, May 14 (Reuters) - A roadside bomb ripped through a vehicle in a convoy of Western troops as it passed over a bridge outside the Afghan city of Herat on Monday, wounding several soldiers, witnesses said. The incident, part of rising violence in recent months following last year's bloodiest fighting since the Taliban were ousted in 2001, prompted the troops to briefly seal off the bridge. One vehicle was badly damaged in the blast. Both NATO and U.S.-led troops operate in Herat, regarded as one of a handful of safe areas in Afghanistan until recent weeks. There was no immediate claim of responsibility, though the Taliban have been behind most of the attacks against Afghan and foreign forces.