Six people died and over 30 others were injured in Bulgaria Wednesday when a powerful blast ripped through a bus carrying Israeli tourists.
The explosion took place at Burgas airport, Xinhua reported.
They had arrived at the airport on an Air Viva flight from Tel Aviv.
"Bulgarian authorities are working on the theory that this was a terrorist attack," the foreign ministry said.
Foreign Minister Nickolay Mladenov expressed his condolences to his Israeli counterpart Avigdor Lieberman and pledged to keep him informed of the details of the incident.