Explosions and gunfire have rocked the north Nigerian city of Damaturu, in a suspected Boko Haram attack that targeted police officers.

A local source confirmed to Al Jazeera that gunmen believed to be Boko Haram fighters attacked the Yobe state University in Damaturu and other targets Damaturu early on Monday morning.

The fighters came from the bush and opened fire, according the witnesses.

The military has engaged them and gunshots were being heard by 08:00 GMT around Damaturu, though the gunfire later moved away from the university and into the bush as Nigerian troops chased the fighters.

Some students and university staff fled to the bush and were holed up there. Residents of the city were largely remaining indoors as the gunfire continued while the military deployed around the area.

It was not immediately clear if there were casualties.

"We have left our homes. We are now in the bush. We don't know what's going to happen," local man Umar Sada, who said a police barracks had been destroyed, told the AFP news agency.

In a separate development, at least five people were killed in two explosions at a marketplace in Maidugari, our correspondent Rawya Rageh, reporting from Abuja, said. 

Monday's attacks come a day after scores of people were reportedly killed after suspected Boko Haram fighters, who arrived on motorcycles throwing bombs, raided Shani town in Nigeria's northeast Borno state. 

Shani is located in Nigeria's Borno state, the heartland of Boko Haram's five-year insurgency, which has displaced more than one million people.

The raid also comes after a suicide bomb and gun attack on the central mosque in the northern city of Kano on Friday which bore all the hallmarks of Boko Haram and left at least 120 people dead.

The armed group is fighting to revive an Islamic caliphate in Nigeria's north. It is suspected to be behind Friday's attack on the central mosque in the second city of Kano, where at least 100 people died.

Source: Al Jazeera and agencies