The gang, armed with AK-47s, stormed the Government Science secondary school in the Kankara district of the state of Katsina at about 9.40pm local time on Friday, police and locals said.

A parent and school employee said roughly half the school's 800 students were missing.

President Muhammadu Buhari said in a statement the military had located the kidnappers in a forest and was exchanging fire with them, aided by air support.

In the statement, Buhari condemned the attack in his home state. Police and the military were still working to determine how many were kidnapped and missing.

Officers at the scene on Friday exchanged fire with the attackers, allowing some students to run for safety, police spokesman Gambo Isah said in a statement.

Police said they would deploy additional forces to support the search and rescue.

One officer was shot and wounded in the exchange of fire with the gang, they said.

Katsina is plagued by violence the government attributes to bandits - a loose term for gangs of outlaws who attack locals and kidnap for ransom.

Attacks by Islamist militants are common in northeast parts of the country.

Australian Associated Press