Three people were killed on Sunday in clashes between security forces and anti-government protesters in southern Yemen, where separatist sentiment is strong, officials and witnesses said. The clashes, which have persisted for several days, prompted a rare call by the United States for an end to the violence it said could undermine the impoverished country's unity. Officials said opposition groups killed two civilians and wounded 20 in protests in the Raffan district of Lahej province near Aden in the south. A member of the opposition Socialist Party said locals were defending themselves from government shelling of villages and farmland. One protester died in Dalea when a grenade exploded in what appeared to be an accident. Independent daily Al-Ayyam said a man was shot dead on Saturday and four wounded in clashes in Habilain, where three died last month after locals objected to new army outposts. Bashrahil Hisham Bashrahil, manager of the group that publishes Al-Ayyam, said the authorities confiscated copies of the paper early on Sunday and detained some employees.