Nigeria's police say they're searching for 35 missing policemen after two attacks on police training camps in northeastern Borno state, which is battling a five-year insurgency by the Boko Haram militant group.

The police force spokesman Emmanuel Ojukwu said Saturday the men went missing after an Aug. 20 attack was carried out on a training camp that led to a gunfight that lasted for several hours. The statement on the police force website says the attack followed another one on Aug. 7 that was repelled by the police.

Ojukwu didn't say who was suspected to have carried out the attack, but the state is the stronghold of the Boko Haram group which targets security forces, government officials and civilians in its campaign to establish an Islamic state in Nigeria.