Clashes broke out late Saturday evening between security forces and demonstrators here, killing one protester and wounding 15, doctors said at a field hospital at the site. Security forces opened fire, said witnesses, in the first direct assault on protesters in the capital since snipers killed 52 protesters more than three weeks ago. The shooting follows a week of violence in a central city, Taiz, where security forces and men in plain clothes have fatally shot about 20 protesters. Saturdays violence began after a group of about 400 protesters tried to march to the presidential palace late in the evening. They were stopped at a major intersection by security forces about a half-mile away from their main sit-in area.