A bus carrying young Israeli tourists in a Bulgarian resort exploded today, killing three people and wounding at least 20, police said.
Witnesses told Israeli media that the huge blast occurred soon after someone boarded the vehicle. Images showed smoke billowing from the scene.
The incident took place in the Black Sea city of Burgas, 250 miles east of the capital, Sofia.
The bus was full of young Israeli travellers.
Bulgaria is a popular tourist destination for Israelis.
Israeli tourists have been targeted before, namely in India, Thailand and Azerbaijan. Iran is suspected of being behind these attacks.
Israeli foreign ministry spokesman Jonathan Rosenzweig said a flight from Tel Aviv had landed at 4.45pm and the blast took place about 40 minutes later.
"We don't know if it was a terror attack," said Paul Hirschson, another spokesman for the ministry. "We do know it was an explosion."
Witness Gal Malka told Israel's Channel 2 TV that she saw someone board the bus before it exploded.
Officials said Israeli foreign minister Avigdor Lieberman had spoken with his Bulgarian counterpart and was being kept abreast of developments.