Authorities imposed a curfew Tuesday in the northern city of Beiji to try to combat a rise in violence there, officials at a joint military center said. No vehicles except ambulances and those used by joint U.S.-Iraqi troops were allowed in the streets as soldiers and police started sweeping the city in a search for insurgents and common criminals. The curfew was announced by American troops on loudspeakers Tuesday morning after prayer. It was not clear how long it would last. Full Story