At least 20 are killed in a bomb blast in northeast Nigeria Tuesday.<br/> <br />A bomb in a van carrying charcoal exploded in a busy market in the latest suspected attack by Islamist militants.<br/> <br />No one immediately claimed responsibility for the blast.<br/> <br />But in recent months, the Islamist group Boko Haram has launched a series of bombings and raids, including the abduction of more than 200 schoolgirls in April.<br/> <br />The military said earlier that it had arrested a number of suspected Boko Haram collaborators it said was involved in the abduction of the schoolgirls.
