Photographs and video taken at the airport in the seaside resort of Burgas showed billowing black smoke from the explosion that left the bus a blackened skeleton, scorched several buses nearby, shattered windows and forced the airport to temporarily close, the New York Times reported. Witnesses quoted by Israeli news media said some victims were on fire as they tried to escape the bus. They said many suffered severe burns and that body parts were flung around the parking lot.
The explosion occurred around 5 p.m., as Israeli tourists who arrived in Burgas on a charter flight boarded buses that were supposed to transport them to a local hotel, Israel's Ynet News reported. The blast took place on only one of the buses.
Bulgarian Interior Minister Tsvetan Tsvetanov said police were investigating two possible causes of the blast: that an explosive device was put in the bus before the tourists boarded or that the explosives were in the tourists' luggage.
"We heard a very strong blast. The bus was full with people and children. Flesh and blood everywhere," a Bulgarian witness told TV7 television, Reuters reported. "I saw another bus catching fire from the one that exploded. It was complete chaos."
The tourists had arrived on a charter flight from Israel and were on the bus in the parking lot outside the Burgas airport when the blast ripped through the double-decker. By late evening, the airport was still sealed off and closed as authorities tried to pin down exactly what had happened.
"We sat down, and, within a few seconds, we heard a huge boom, and we ran away. We managed to escape through a hole in the bus," Aviva Malka told Israeli Army Radio from the scene.
The Bulgarian Interior Ministry declined to comment on whether it might have been a suicide attack, as some witnesses had speculated, and said it was questioning people who had been close to the scene.
Bulgarian President Rosen Plevneliev said that during a meeting held about a month ago, Mossad representatives did not warn Bulgarian officials of the possibility of a terror attack, the Sofia News Agency reported.
Plevneliev stressed that Bulgarian authorities took all the appropriate measures to protect the terror attack victims.
The explosion comes on the 18th anniversary of a 1994 bomb attack on the headquarters of Argentina's main Jewish organization by an Iranian-backed Hezbollah suicide bomber, which killed 85 people.
Israeli Prime Minister Benjamin Netanyahu blamed Iran and said Israel would respond.
"All the signs lead to Iran. Only in the past few months we have seen Iranian attempts to attack Israelis in Thailand, India, Georgia, Kenya, Cyprus and other places," Netanyahu said in a statement.
"Eighteen years exactly after the blast at the Jewish community center in Argentina, murderous Iranian terror continues to hit innocent people. This is an Iranian terror attack that is spreading throughout the entire world. Israel will react powerfully against Iranian terror," he said.
Iran had no immediate comment on Israel's accusations, and no group claimed responsibility for the blast, which the Bulgarian foreign minister said was caused by a bomb placed in the bus' luggage compartment. But if the Israeli accusations are confirmed, the Bulgarian blast would be the first successful attempt by Iranian operatives to kill Israelis in attacks abroad after a string of failed bomb plots targeting Israeli diplomats in Georgia, India and Thailand this year.
The explosion came only a few days after a suspected operative of Hezbollah, the Lebanese militant group with close ties to Iran, was arrested in Cyprus on suspicion of plotting to kill Israeli tourists there. That was big news in Israel and reinforced the sense of suspicion that Israelis vacationing abroad might be targets.
Still, the deputy foreign minister of Israel, Danny Ayalon, was quoted on Israel's Channel 2 television as saying there was no warning of the Bulgaria attack.
The Bulgarian Foreign Ministry said on its website that the country's president, foreign minister and interior minister rushed to the scene and that the authorities were working on the theory that the explosion was a terrorist attack but did not specify who might be responsible.
In the capital, Sofia, home to most of the 5,000 Bulgarian Jews in the overwhelmingly Christian country of 7.4 million people, the mayor ordered police deployments in all public places linked to the Jewish community, the Associated Press reported.
In Washington, President Obama said in a statement that he strongly condemned "today's barbaric terrorist attack on Israelis in Bulgaria," but he did not specifically accuse Iran.
Burgas is Bulgaria's fourth largest city and lies on the Black Sea coast some 40 miles from the border with Turkey. It is at the center of a string of seaside resorts, which are popular for their sunshine and low cost compared with many parts of the Mediterranean.
With a population of about 200,000, it is also an important industrial hub and has Bulgaria's sole oil refinery.
"Such a terrifying act on the territory of a sovereign country, member of the EU, is a provocation to the efforts of the democratic community for achieving world peace," said Bulgarian Prime Minister Boiko Borisov.
The chief mufti of Bulgaria's Muslims, who account for about 10 percent of the Balkan population, also condemned the attack, as did the EU and British and French foreign ministers.
Burgas airport was closed after the incident and flights were redirected to the airport of Varna, police said. Tourists were stranded at the airport as it was checked for other explosive devices, Focus news agency reported.
Israel's flag carrier El Al cancelled its flight from Tel Aviv to Sofia that was due to leave at 1600 GMT, a spokeswoman told Reuters. Nothing had been decided about Thursday's flights.
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