Israel Says Iran is Behind DeadlyBlast in Bulgaria

Israel accused Iran of orchestrating the bombing of a bus packed with Israeli tourists in a Bulgarian resort town Wednesday that killed at least six people and injured 30 others, adding to tensions across the Middle East.

Fire engulfed the bus and nearby vehicles in an airport parking lot in Burgas, on Bulgaria's Black Sea coast, sending up plumes of dark smoke. Israel's foreign minister, Avigdor Lieberman, said his Bulgarian counterpart told him a bomb was planted on the bus.

Israeli Prime Minister Benjamin Netanyahu promised retaliation.

"This is an Iranian terror attack that is spreading throughout the entire world," he said. "Israel will respond with force."

Mr. Obama called Mr. Netanyahu by phone to extend his condolences.

Tehran didn't immediately issue any comment. No group immediately claimed responsibility.

The bus bombing follows accusations by U.S. and allied governments that Iran's elite military unit, the Islamic Revolutionary Guard Corps, has been behind plots to hit Western targets in Kenya and Cyprus over the past month. The Obama administration didn't explicitly accuse Iran in Wednesday's attack.

The White House is worried that alleged aggression by the Revolutionary Guard's overseas unit, the Qods Force, is partly in response to intensifying Western sanctions targeting Iran's oil revenues and finance sectors. "We're definitely seeing stepped-up activities," said a senior U.S. official. "We're guarding against this closely."

U.S. officials also believe Iran is retaliating for the assassinations over the past three years of five Iranian nuclear scientists, which Iran blames on Israel.

Since the start of this year, Israeli diplomatic missions and Israeli tourists have been targeted in a series of plots—many of which have been thwarted—in countries stretching from Thailand to Georgia.

The U.S. and Israel have linked the incidents to Iran and the Iranian-backed militia, Hezbollah.

U.S. officials believe the Islamic Revolutionary Guard Corps is increasingly dominating Tehran's foreign policy, particularly as sanctions threaten to cripple the Iran economy. One U.S. official said the IRGC was acting with more autonomy within the Iranian hierarchy: "The leash has been loosened."

Wednesday's attack came as escalated fighting in Syria threatens to alter the dynamics of the conflict. Israel fears Hezbollah and Iran will take advantage of chaos in Syria to launch cross-border attacks into the Jewish state.

The Burgas attack fits the pattern of recent plots against Israelis abroad.

Last week, Cypriot officials arrested a Lebanese man, allegedly tied to Hezbollah, on suspicion he was preparing to attack Israeli tourists at the resort of Limassol.

Earlier this month, Kenyan authorities arrested two Iranian men on charges of illegally shipping roughly 100 kilograms of high explosives into the country. They also charged the men with conducting surveillance on U.S., British and Israeli targets in the Kenyan capital of Nairobi and the resort of Mombasa.

"It's obvious there is an Iranian campaign," said Shmuel Bar, an Israeli counterterrorism expert at the Interdisciplinary Center at Herzlya.

"It has to do with dissuading Israel by sending a message that if there's an Israeli attack on Iran, then we can cause problems…It's a form of pre-emptive deterrence."

The beach resort that was hit in eastern Bulgaria has become an increasingly popular vacation spot for Israelis as tensions between Israel and Turkey have mounted.

The 5:30 p.m. blast struck soon after a plane of vacationers from Tel Aviv landed and passengers had boarded buses hired to shuttle them to their hotels. Israeli authorities reported that seven people died. Bulgarian authorities have confirmed six dead.

"I was on the bus and heard a big boom," said Gal Malcha, an Israeli survivor interviewed by Israel's Channel 2 news. "We got out by a hole made from the explosion."

After the explosion, Bulgaria stepped up security for the Jewish community in the Bulgarian capital Sofia, home to most of the country's 5,000 Jews.

The attack coincided with the anniversary of the bombing of a Jewish community center in Buenos Aires 18 years ago that killed 85 people.

An Argentine magistrate concluded Iran was behind that attack.

Israel has for months threatened to attack Iran's nuclear installations if Western diplomacy doesn't force Tehran to stop its production of nuclear fuel

But despite Mr. Netanyahu's pledge of revenge, it is unlikely that Israel would use Wednesday's attack as grounds to strike Iranian nuclear targets, a move opposed by the U.S. and likely to trigger a regional war.