An explosion rocked a bus full of Israeli tourists in Bulgaria Wednesday, killing at least seven people and wounding more than 30.

The blast took place at an airport in the Black Sea resort city of Burgas.

A plane carrying many young people had recently arrived from Tel Aviv, and the tourists were boarding buses to go to their hotels.

Israeli Prime Minister Benjamin Netanyahu said "all signs point to Iran" as the instigator of the attack. He promised a strong response.

Earlier this year, officials in Jerusalem asked for more security for their citizens traveling in Bulgaria.

They suspected terror attempts by Iranian-backed terror groups such as Hezbollah.