MAIDUGURI, Nigeria (Reuters) - Nigerian security forces used helicopter gunships to destroy a camp belonging to the Islamist sect Boko Haram in forest in the northeast on Friday, killing 17 of them in a battle, they said.

A statement from joint military and police forces in northeast Borno state also said one of their number was killed in the exchange of fire, which cast fresh doubt on a ceasefire declared by one Boko Haram commander this week.

(Reporting by Ibrahim Mshelizza; Writing by Tim Cocks; Editing by Jon Boyle)