Armed men stormed a college in north-west Nigeria in the early hours of Friday morning, opened fire and kidnapped an unknown number of students, a police spokesman told CNN. 

The students were abducted from the Federal College of Forestry Mechanisation, Mando, Kaduna. 

It is the third mass kidnapping from a school in northern Nigeria this year and police say they are working to rescue the students. 

"The police and the military are on top of the situation. We are trying to liaise with the school management to know the exact number of students that were abducted and then see the possibility of rescuing them unhurt and arresting the perpetrators," Kaduna police spokesman Mohammed Jalige said.

Jamilu Abdullahi is a student at the college and told CNN he heard the attackers shooting when they arrived at around 3 am. 

Abdullahi said the armed men made a beeline for the female hostel, even though the male dormitory is nearer the fence where they came in. 

"We saw them and ran away... the bandits came and were firing their guns and took away the girls. We are as yet not certain the number of those kidnapped but I know that there are about 80 to 100 girls in that hostel," he said. 

This abduction is the latest in a string of similar kidnapping cases. More than 300 schoolgirls were kidnapped from a school in Zamfara State, also in northwest Nigeria, earlier this month. 

At least 42 people were abducted from a state-run school last month in Kagara, Niger State and later released, and more than 300 schoolboys were taken and later freed in December.

Kidnapping for ransom is rife in parts of Nigeria and has become a major security challenge.

State governors regularly pay ransoms to secure the safety of victims but rarely admit to doing so. 

Nigerian President Muhammadu Buhari recently told state governors to review "their policy of rewarding bandits with money and vehicles," saying the policy "could backfire with potentially disastrous consequences."

Buhari also urged governors to work hard to secure their schools.