WBRZ - Baton Rouge

MAIDUGURI, Nigeria - A witness and officials say at least 20 people have been killed in an attack by Islamic extremists on a military base in northeast Nigeria.

A military spokesman says all those killed were believed to be fighters from the radical Islamic terrorist network Boko Haram. However, witnesses said at least one of the dead appeared to be a civilian.

Military officials in Nigeria routinely downplay civilian casualties. An Associated Press journalist could not immediately reach the area Sunday.

Boko Haram and its splinter groups are waging a bloody guerrilla campaign against Nigeria's weak central government.

In a new video, the group's leader denies taking part in any peace talks with Nigeria's government. He vows that the group will continue attacks until Nigeria is ruled by Islamic law. He also threatened the man claiming to be a leader of Boko Haram who has said the group wants to negotiate a cease-fire with Nigeria's security forces.