ABUJA, May 8  -- At least 50 people, mostly students, were injured as gunfire and two explosions rock Nigeria's northeastern state of Yobe on Friday, witnesses and hospital sources told Xinhua.

The attack started with a suicide bomb, in which the bomber blew himself up prematurely in the car park of the College of Administrative and Business Studies in Potiskum, the largest city in the restive Yobe State, a witness said.

A second explosion in the college dormitory harmed no one, as the students had all gone out to their classrooms, a local security officer who rushed to the scene said in the local Hausa language.

This was followed by a gunfire aiming at the students on the main campus, said the security officer who insisted on anonymity.

Hospital sources told Xinhua that, so far, 50 injured people have been admitted, 45 of them said to have sustained injuries as they fled the attack scene. Five others had bullet wounds, according to a senior medical officer.

The attack, suspected to be a perpetration of Boko Haram, was quelled by security operatives who arrived the scene after a distress call.

Boko Haram - which seeks to enshrine the Islamic Sharia law in the constitution of Nigeria, Africa's most populous country - is currently being routed by Nigerian forces who launched an aerial bombardment last week to dislodge the terrorists from their den.