ABUJA, Jan. 16 (Xinhua) -- A suicide bomber attacked the University of Maiduguri located in the capital of Nigeria's northeastern state of Borno early Monday, killing at least five people and injured more than 15 people, local police confirmed to Xinhua.

There were two blastes. The first one ripped through the mosque where professors were saying dawn prayers and at least one is among victims, according to a student. The second bomb went off at an entrance gate, said a university worker. Both spoke on condition of anonymity for their safety.

Police Commissioner Damian Chukwu said 5 people died in the explosion at the mosque, including a university professor, and 15 wounded people have been evacuated to hospitals. It was not clear if the explosions came from suicide bombers or were planted bombs, police said.

Maiduguri has been attacked many times but this is the first attack on the university blamed on Boko Haram — the Islamic extremist group whose name means "Western education is sinful."

It is the first major attack since Nigeria' President Muhammadu Buhari last month declared that Boko Haram was "crushed," after troops destroyed their stronghold in the Sambisa Forest in northeastern Nigeria.

Nigeria's army said Sunday that troops continuing "clearance operations of remnants and fleeing Boko Haram terrorists" killed several insurgents and rescued 58 kidnap victims, mainly women and children last week. One soldier was injured, it said.

Nigeria's 7-year-old Islamic uprising has killed more than 20,000 people.