Residents in Nigeria's northeastern Borno state say three separate blasts shook the town of Maiduguru on Tuesday.
Witnesses say the blasts struck two police stations and a government building in the state capital. They also reported hearing gunfire after the explosions.
Authorities did not immediately name suspects in the attack.
The radical Muslim sect Boko Haram has been blamed for similar violence targeting police and religious and political leaders in recent months.
Earlier on Tuesday, police blamed Boko Haram for the shooting death of a rival cleric in the town of Biu, north of Maiduguru.
Authorities said gunmen riding motorcycles killed Sheik Ibrahim Birkuti outside his home.
Birkuti had been critical of Boko Haram's use of violence, which has largely taken place in Borno state.
The group is fighting to establish Islamic law across Nigeria. Its name means "Western education is sinful."
Some information for this report was provided by AP, AFP and Reuters.