Bulgarian citizens are advised against traveling to Turkey for the moment, the Foreign Ministry in Sofia has said.
In a statement, it has cited the "deteriorated security environment", also urging Bulgarians in Turkey to avoid visiting "lively places" in big cities in the aftermath of the attempted coup last week.
"A series of operations are being conducted by the Turkish security forces, as a result fo which tensions could escalate and threats could emerge for the physical security of citizens."
Turkey has stepped up security in Edirne, the first big city for those approaching Istanbul from Europe and not far from the Bulgarian border, the ministry says.
Identity checks and document inspections for vehicles are being constantly carried out on the roads into and out of Edirne.
The same applies to border controls on the Turkish side of the common frontier, according to the Bulgarian diplomatic service.