A suicide bomber attacked a police checkpoint at the entrance to a university in the city of Ramadi on Monday, killing three people and injuring seven others, police and witnesses said. The Associated Press quoted witnesses as saying that the dead were students from Anbar University. Police said they had not determined whether the suicide bomber was wearing a belt laden with explosives or was driving a booby-trapped car. A curfew was imposed in the area. Also Monday, another suicide bomber blew up at an Iraqi army checkpoint south of the city, and clashes then erupted between gunmen and soldiers, a police officer said on condition of anonymity. Mortars exploded in the area, he said.