Suspected Boko Haram fighters attacked a business school in northeast Nigeria on Friday with gunfire and two bomb blasts.

A suicide bomber detonated explosives prematurely in the car park of the College of Administrative and Business Studies in Potiskum, according to a security officer and a hospital worker, who spoke on condition of anonymity to the Associated Press news agency.

A second bomb exploded in the college dormitory, but all the students apparently were already in classrooms.

Five students were wounded by gunfire and another 45 people are being treated for injuries sustained as they jumped out of windows and over walls to escape the attackers, the hospital worker said.

Those injured include schoolchildren from the neighbouring Government Science Secondary School, who also thought they were under attack.

At least 40 students were killed when Boko Haram attacked that school last year.

In Friday's attack, the gunmen arrived around 8 am (0700 GMT) and opened fire at the gate of the business school, witnesses said. Security guards armed only with clubs ran away, said the witnesses who spoke to AP on condition of anonymity for fear of reprisals.

It is the first school attack reported since a multinational offensive drove Boko Haram out of towns and villages seized last year where the armed group, who have sworn allegiance to the Islamic State of Iraq and the Levant group, declared an Islamic caliphate.

Troops from neighbouring countries joined the fight as Nigeria's home-grown armed group began attacking across borders.

Nigeria's military says the main fighting force of Boko Haram has fled to strongholds in the vast Sambisa Forest of northeast Nigeria, where Nigerian troops this month rescued nearly 700 girls and women held in captivity by the fighters and destroyed about 20 camps.

Source: Al Jazeera