"Eight people were killed in the house by the mob over the alleged blasphemy," Zamfara state police spokesman Shehu Mohammed told AFP of the incident, which happened on Monday.
He said the mob of Muslim students in the town of Talata Mafara were enraged over alleged derogatory comments by their Christian schoolmate, who they attacked.
He said the victim was rescued by a passerby, a Muslim who rushed him to the police station for safety.
"The man who rescued the student and his wife were not among the dead," the police spokesman said.