Borno state police commissioner Tanko Lawan said some of the girls were abducted Monday night from a school in Chibok, on the edge of the Sambisa Forest that is an insurgent hideout.
A State Security Service official said gunmen killed a soldier and police officer guarding the school and took off with at least 100 students.
Islamic extremists have been abducting girls to use as cooks and sex slaves.
Extremists also are blamed for Monday morning's explosion at a busy bus station in Nigeria's capital that killed at least 75 people and wounded 141.
