The radical group Boko Haram has attacked Maiduguri, a north-eastern metropolis of more than 1 million people, Nigeria's Defence Ministry said Sunday, dpa reported. The army and air force were repelling the simultaneous attack on the capital of Borno state and the nearby city of Monguno, it said on Twitter. The fighting began Saturday night after hundreds of militants tried to invade Maiduguri, security officials were quoted as saying by the Premium Times newspaper. No information on casualty figures was immediately available. A curfew was imposed on the state capital, the Defence Ministry said.