Updated

Boko Haram extremists are suspected of attacking a business school with two bomb blasts and gunfire Friday in northeast Nigeria.

A suicide bomber died when he blew himself up prematurely in the car park of the College of Administrative and Business studies in Potiskum, a security officer and a hospital worker told The Associated Press. Both spoke on condition of anonymity because they were not authorized to speak to reporters.

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 told AP.

Those injured included schoolchildren from the neighboring Government Science Secondary School, who also thought they were under tack. At least 40 students were killed when the terror group attacked that school last year.

The gunmen arrived around 8 a.m. local time Friday. They 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 reporters on condition for fear of reprisals.

It is the first school attack reported since a 3-month-old multinational offensive drove Boko Haram out of towns and villages seized last year where the insurgents, who have sworn allegiance to the Islamic State group, declared an Islamic caliphate. Boko Haram means "Western education is sinful."

Troops from neighboring countries joined the fight as Nigeria's home-grown Islamic extremist 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 insurgents and destroyed about 20 camps.

The Associated Press contributed to this report