seven people were killed and more than 20 injured by an explosion on a bus carrying Israeli tourists outside the airport of the coastal city of Burgas yesterday, Israeli authorities said.

The mayor of the city, on the Black Sea coast, said the bus was carrying Israeli tourists, but police could not immediately confirm their nationality. Police said several other buses at the site had been damaged.

The Bulgarian foreign ministry had put the death toll at six, with 32 people wounded.

An Israeli witness told Israeli army radio that the explosion was probably caused by a suicide bomber at the entrance of the bus.

Bulgarian police said they were investigating and could not say at this point what caused the explosion.

Burgas airport was closed after the incident and flights were redirected to the airport of Varna.

Israeli officials had previously said that Bulgaria was vulnerable to attack by Islamist militants who could infiltrate via Turkey.