The email, sent to schools in several cities, claimed that a powerful explosive device had been placed inside a plastic bag and was equipped with a remote trigger, Anadolu Agency reported.
The message included threats of violence against Italians and was signed by a person claiming to be the leader of a group called the Vilayat of Misoginistan.
Law enforcement officers were carrying out security checks at the affected schools. The number of schools reporting threats was still rising.
The incident follows a similar scare in recent days, when an email containing threats was sent to 280 school principals.