Police in Plovdiv are checking reports of explosive devices at kindergartens and government offices in the city, the regional police directorate told BTA.
The threats were sent electronically. The sites named include the district prosecutor's office in Plovdiv and the regional governor's office.
Police sent patrols to the addresses as soon as the reports came in and are following the set procedure, the directorate said.
Similar reports of explosive devices have come in from other Bulgarian cities.