The Bulgaria bus blast that has killed at least eight people was carried out by a suicide bomber belonging to the Iran-backed Hezbollah fighters of Lebanon, according to Israeli defence minister Ehud Barak.
"The immediate executers are Hezbollah people, who of course have constant Iranian sponsorship," Reuters quoted Barak as telling Israeli radio.
He added that the government will do everything to find the perpetrators and bring them to justice. Barak also denied that any early warnings were received, as claimed by Bulgarian President Rosen Plevneliev.
Out of the eight people dead so far, six were Israelis, who were part of a large tourist group which had flown in on a chartered flight.
Earlier, Israeli prime minister Benjamin Netanyahu released a strong statement saying Iran was behind the blast, which took place on the anniversary of the 1994 Hezbollah bombing which killed 85 people in Argentina.
"All signs point towards Iran. Over the last few months we have seen Iran's attempts to attack Israelis in Thailand, India, Georgia, Kenya, Cyprus and other countries. This is a global Iranian terror onslaught and Israel will react firmly to it," said Netanyahu.
Iran is yet to officially respond to the accusation.
Meanwhile Bulgaria's interior minister, Tsvetan Tsvetanov, claimed that his country has identified the bomber. He is quoted by Reuters as saying:
"We have established a person who was a suicide bomber in this attack. This person had a fake driving licence from the United States."
The Israeli government has sent special planes to collect the bodies of the victims, and also treat the injured. Up to 34 people are thought to have sustained injuries in the attack, and several have spoken to reporters about their experiences.
One survivor, Gal Malka, told Israeli army radio: "I was on the bus and we had just sat down, when after a few seconds we heard a really loud explosion. The whole bus went up in flames."
Another eyewitness of the incident said: "People who survived the blast escaped through the windows, so as not to walk over corpses."
First-hand witness accounts added that after the bus went up in flames, people started crowding the scene. Decapitated heads were visible while some saw flying body parts, according to the BBC.