JERUSALEM, July 18, 2012: Israel accused Iran on Wednesday of being behind a deadly attack against Israeli tourists at an airport in Bulgaria, which killed at least four people and wounded dozens of others.

There was no immediate confirmation of the nationalities of the dead or the injured, but Israel's foreign ministry said the blast had targeted a bus carrying Israeli tourists who had just landed at the port city of Burgas on the Black Sea.

"All the signs point to Iran," Prime Minister Benjamin Netanyahu said in a statement, which claimed this was the latest in a string of attempts to attack Israelis in Thailand, India, Georgia, Kenya, Cyprus and other places.

Netanyahu noted that the attack fell on the 18th anniversary of an attack on a Jewish community centre in Buenos Aires that killed 85 people and wounded around 300.

The 1994 attack was blamed on Iran, which denied the charges.

"Israel will respond forcefully to Iranian terror," Netanyahu warned.

Defence Minister Ehud Barak also condemned the blast as "very serious" and vowed that Israel would hunt down those behind it.

"For some time we have been following the intentions of terror organisations like Hezbollah, Hamas and Iranian and Jihad elements, to carry out terror throughout the world," he said in a statement.

"The security establishment will act with all its strength to get to those who carried out this attack and those who sent them."

Israel's foreign ministry said the attack targeted a group of tourists who had just landed on a flight from Israel shortly before 5:00 pm (1400 GMT).

"Some time close to 5:00 pm there was a flight that landed in Burgas, the passengers went onto a bus and then there was an explosion that we don't know the source of," said ministry deputy spokeswoman Ilana Stein.

"What we know is that there are casualties and probably not only injured but also dead. We know that some were Israelis but we don't know if all of them were," she told AFP.

Israeli media reports said there were around 40 tourists on the bus at the time of the blast, many of them young Israelis who were en route to a tourist resort.

Speaking to army radio, two Israeli tourists who were at the scene described the moment the blast occurred.

"I was on the bus and we had just sat down when after a few seconds we heard a really loud explosion," Gal Malka told the station by phone from the airport, saying the explosion took place just outside the front of the bus.

"The whole bus went up in flames," she said.

Aviva, another Israeli woman who was on a nearby bus, said she heard a "very loud explosion" and described seeing at least seven dead bodies.

"There are seven dead people," the woman told the radio, adding that she saw people whose clothes had been blown off by the blast and bodies lying on the floor.

"It was just terrible; people were jumping out of the windows," she said.

Shortly after the attack, Foreign Minister Avigdor Lieberman spoke with his Bulgarian counterpart, and four Israeli diplomats were en route to Bulgaria to help out, the ministry said.

Medics from Israel's Magen David Adom emergency services were also preparing to fly out to help with the treatment and repatriation of wounded Israelis, the organisation said.