Nigerian troops killed five suspected Islamists and recovered arms and explosives in a raid in the restive northern city of Kaduna, the military said Friday.

Army spokesman in Kaduna Colonel Sani Usman said two suspected Boko Haram members were also wounded during the operation, a raid on a bomb-making factory in Rigasa area of the city on Thursday.

"On approaching the factory, some suspected terrorists opened fire and also threw already primed IED (improvised explosive device) at the troops.

"The exchange of fire that ensued resulted in the death of five terrorists, while two that sustained various degrees of injuries are being treated." he said.

Soldiers destroyed the bomb factory and recovered several guns, rifles and other bomb-making chemicals, he added.

Kaduna is considered a stronghold of Boko Haram, which has repeatedly targeted the security services and churches as part of its violent campaign across northern and central Nigeria.

Nigerian troops have carried out a series of raids on suspected Boko Haram hideouts in recent months as violence linked to the sect's insurgency is believed to have left some 3,000 people dead in Nigeria since 2009, including killings by the security forces.