About 20 people have been killed and 90 wounded in a bomb blast at a mosque in the northern Nigerian city of Maiduguri. The blast comes just a day after the army fought Boko Haram militants in the west of the city. Now, Maiduguri is the capital of Borno state and the birthplace of Boko Haram's campaign to create an Islamic state in northeast Nigeria, Africa's most populous country. As yet, there has been no immediate claim of responsibility for Monday's attack but the blast bares the hallmarks of Boko Haram, whose insurgency has killed thousands and displaced some 2.1 million people in the region. Monday's blast happened in a western suburb where the army had exchanged fire on Sunday with suspected Boko Haram fighters who it said had tried to slip into Maiduguri to stage suicide attacks.