Bomb threats also reached the Defence Ministry's work email accounts in October, Defence Minister Dimitar Stoyanov said. He said it is not clear where they were sent from or what the IP address of the device was.

Stoyanov was replying to a parliamentary question from Ivelin Parvanov, an MP from the Vazrazhdane party. Parvanov asked about a "series of bomb threats" against public buildings and offices in early October, whether the ministry had received any, and whether staff had to be evacuated.

The threats against the ministry building at 3 Dyakon Ignatiy Street in Sofia arrived by email on 5, 6 and 7 October. They were sent to work contact addresses listed on the official website. Staff were not evacuated after checks and searches of the building.

Nine other threats were sent by email to state kindergartens in Karlovo and Stara Zagora, which fall under the Military Clubs and Military Recreation Executive Agency. Staff there were led out and security was stepped up at the buildings.

In every case, the steps were taken together with Interior Ministry officers, the minister said. Officers searched and checked the sites, and there are records of this. All the information has been passed to the organised crime directorate (GDBOP) and the Interior Ministry.