ABUJA: Nigerian President Muhammadu Buhari on Wednesday condemned the abduction of schoolboys from a school in central Nigeria and ordered a rescue operation, his office said.

"The President has directed the Armed Forces and Police, to ensure immediate and safe return of all the captives," presidential spokesman Garba Shehu said in a statement.

The number of students and staff abducted from the school in Kagara, Niger state, was still unknown, the statement added.

Gunmen belonging to criminal gangs were believed to be behind the attack that took place late on Tuesday.

Buhari, 78, was elected in 2015 on promises to crush a bloody jihadist insurgency in northeastern Nigeria, but his armed forces have struggled against the militants as well as worsening security across the country.

Heavily-armed gangs known locally as "bandits" active in northwest and central Nigeria have stepped up attacks in recent years, kidnapping for ransom, raping and pillaging.

The president urged Nigeria's security forces on Wednesday "to do all that can be done to bring an end to this saga, and avoid such cowardly attacks on schools in the future."

Only two months ago, more than 300 students were kidnapped in nearby Katsina state.

The boys were later released but the incident sparked global outrage.