World leaders have called for justice after a bomb killed at least six Israelis and left thirty injured.
William Hague and Barack Obama both spoke out after the attack which ripped through a bus carrying Israeli tourists at Burgas Airport in Eastern Bulgaria.
The group had arrived at 4:45pm and explosion happened 40 minutes later.
Early witnesses reported a person boarded the coach shortly before it exploded, but later Bulgarian Foreign Minister Nikolai Mladenoc said that the explosion was caused by a bomb in the trunk of the bus.
Israeli Prime Minister Benjamin Netanyahu was quick to blame Iran for the bombing:
Five people died in the blast and casualties were rushed to nearby hospitals where another died bringing the death toll to six.
Foreign Secretary Willam Hague offered condolences to those affected and Barack Obama called for justice, describing the attack as, "completely outrageous."
The White House issued a statement stressing their commitment to Israeli security.
The explosion comes on the 18th anniversary of a 1994 bomb attack on the headquarters of Argentina's main Jewish organisation by an Iranian-backed Hezbollah suicide bomber, which killed 85 people.
Israeli officials had previously said that Bulgaria, a popular holiday destination for Israeli tourists, was vulnerable to attack by Islamist militants who could infiltrate via nearby Turkey.