Israel vowed to strike back at Iran for a brazen daylight bombing that killed eight people on a bus full of tourists in Bulgaria.
Yesterday's bombing was the latest in a series of attacks blamed on Iran that have targeted Israelis and Jews overseas and threatened to escalate a shadow war between the two arch-enemies.
Iran has denied involvement in the past but did not comment on the latest attack.
US president Barack Obama described the bombing as a "barbaric terrorist attack" and called Israeli prime minister Benjamin Netanyahu to pledge help in finding the perpetrators.
The blast destroyed the bus at the airport in the quiet Black Sea resort city of Burgas, 250 miles east of the capital Sofia, where the Israelis had just arrived on a charter flight from Tel Aviv carrying 154 people, including eight children.
Black smoke billowed into the sky from the stricken bus after the bomb exploded. Young Israelis said they were just boarding when the blast ripped through the white vehicle in the airport car park.
Seven people were killed yesterday and Israel's Foreign Ministry said today another casualty, a man, had died of his injuries.
Ministry spokesman Lior Ben Dor said six Israelis were killed and 32 people were wounded. Israeli media said the other two victims who died were Bulgarians.
"We were at the entrance of the bus and in a few seconds we heard a huge boom," said Gal Malka, a teenager who was slightly wounded.
The resort town has become a popular travel destination in recent years for Israelis, particularly for recent high school graduates before they are drafted for mandatory military service.
No group immediately claimed responsibility for the attack, which wounded 30 others. But suspicion immediately fell upon Iran and its Lebanese proxy, the Hezbollah guerrilla group.
"All signs point to Iran," Mr Netanyahu said. "Just in the past few months, we have seen attempts by Iran to harm Israelis in Thailand, India, Georgia, Kenya, Cyprus and more.
"This is an Iranian terror attack that is spreading across the world. Israel will react forcefully to Iran's terror."
The Israeli leader gave no evidence to back his claims.
Israeli security chiefs were meeting late last night and officials said they were still considering options on how to respond.
They said any reaction would probably be a pinpoint operation limited in scope, most likely under the auspices of the Mossad spy agency.
The sources said security officials were also concerned about further attacks, similar to a string of incidents in India, Georgia and Thailand earlier this year, and were reviewing security at potential Israeli targets, such as airline terminals and diplomatic installations.
The Bulgaria attack came exactly 18 years after the bombing of a Jewish community centre in Argentina that killed 85 people. An Argentine investigation concluded Iran was behind that attack.
The violence also came against the broader backdrop of the international stand-off with Iran over its nuclear aims. Israel, accusing Iran of developing nuclear weapons, has repeatedly hinted it is prepared to strike Iranian nuclear targets if Tehran does not curb its suspect programme.
In the past, Iran has accused Israel of being behind a series of covert attacks on Iranian nuclear targets, ranging from the assassinations of nuclear scientists to mysterious computer viruses that have damaged centrifuges.
Israel has never admitted to involvement, but it and others have accused Iran of reprisal missions, including a February bombing in New Delhi that wounded an Israeli diplomat's wife and the discovery of a cache of explosives in Bangkok that Thai officials claim was linked to a plot against Israeli diplomats.