Hundreds of students are missing  after gunmen attacked a school in the northern Nigerian state of Katsina, police said on Saturday.

Gunmen, armed with AK-47s, attacked the Government Science secondary school in Kankara late on Friday, according to state police spokesman Gambo Isah.

"Search parties are working with a view to find or rescue the missing students," a police statement said.

Roughly half of the school's 800 students were missing, Reuters cited a parent and school employee as saying.

Military, police and air force exchange fire

President Muhammadu Buhari said in a statement that the Nigerian military had located the attackers and was exchanging fire with them in a forest, aided by the country's air force.

Police at the scene on Friday also exchanged fire with the gunmen, allowing some 200 students to run for safety, Isah said, adding that police would deploy additional forces to assist in search and rescue operations. One officer was shot and wounded during the exchange, police said.

Police and the military were still working to determine how many students were kidnapped and missing.

The gunmen are believed to belong to groups of bandits in the troubled region and are known to carry out kidnappings for ransom.  Attacks on locals by Islamist militants have also become common place in northeastern parts of Nigeria.

In April 2014, jihadist group  Boko Haram kidnapped 276 girls from their school dormitory in Chibok, Borno State. About a hundred of them are still missing.

mvb/shs (Reuters, dpa)