- Israeli foreign ministry says bus was carrying Israeli tourists
- Israel TV reports gunfire, explosions outside Burgas airport
- Ministry says it is unclear whether there was an attack
(CNN) -- At least three people were killed in an explosion on a bus outside Burgas airport in Bulgaria, an interior ministry spokeswoman said Wednesday.
The Israeli foreign ministry said that the explosion occurred on a bus carrying Israeli tourists from the airport on Bulgaria's Black Sea coast and that there were a number of casualties.
It is not clear whether the explosion was the result of an attack, the foreign ministry said.
Vania Valkova, director of the Bulgarian interior ministry press office, was not able to confirm the nationalities of those killed.
The tourists' plane landed in Bulgaria at 5 p.m., the Israeli foreign ministry said. Valkova said the bus was in the parking zone when the blast occurred.
Israel's Channel 10 station reported that there had been a combined attack of gunfire and explosives outside Burgas airport.
Guy Ailer of Israel, who said he was on a nearby bus, told Channel 10 he saw bodies and injured people at the scene after the explosion.
CNN's Stephanie Halasz and Jennifer Deaton contributed to this report.
