"The bomb was planted and the van drove over it, exploding and injuring eight policemen," said Colonel Victor Ebhaleme, operations commander for a military-police task force in the northeastern city.

"The bomb was from all indications planted by members of Boko Haram that have been engaged in such attacks."

An emergency source said there had been reports of shootings by the military as well, with a number of innocent civilians killed, though he could not yet provide details.

"The situation is very scary," he said on condition of anonymity. "It's terrible. Everybody is thinking about their lives."

Copyright AFP (Agence France-Presse), 2011