Update: Israelis killed in Bulgaria bomb blast, Netanyahu blames Iran

Prime Minister Benjamin Netanyahu blamed Iran for a deadly attack on Israeli tourists in Bulgaria on Wednesday, warning his country would "respond forcefully" to strikes by Tehran.

"All the signs lead to Iran," the Israeli leader said in a statement on the blast which Bulgarian officials said killed three people.

"In the past few months we have seen attempts by Iran to harm Israelis in Thailand, India, Georgia, Kenya, Cyprus and other places," he said, describing it as another stage in "an Iranian terror attack which is spread across the entire world."

"It is exactly 18 years since the bomb attack on the Jewish community center in Argentina, and murderous Iranian terror continues to harm innocent people," Netanyahu said of a 1994 attack in Buenos Aires which left 85 people dead and 300 injured, and which was blamed on Iran.

"Israel will respond forcefully to Iranian terror," he vowed.

Three people were killed and more than 20 injured by today's explosion on a bus carrying Israeli tourists outside the Burgas airport, Bulgarian News Agency (BTA) reported.

The agency added that the exact number of casualties is not yet known.

“The scene has been cordoned off. An on-site investigation has yet to find out the exact cause of the accident — technical, human error, or an act of terror. The airport has suspended operation and flights are being redirected to Varna Airport,” BTA continued.

Reuters reported that several other buses at the site had been damaged in the blast, according to police.

"Initial information shows three people have died, and there are many injured," a spokeswoman for the Interior Ministry said.

An Israeli witness said in an interview with Israeli army radio that the explosion was probably caused by a suicide bomber at the entrance of the bus.

Bulgarian police responded that they were conducting investigations and could not say at this point what caused the explosion.

Israeli officials had previously said that Bulgaria, a popular holiday destination for Israeli tourists, was vulnerable to attack by Islamist militants who could infiltrate via nearby Turkey.