According to Israeli officials, a bomb explosion killed at least seven people on a bus carrying Israeli tourists in the eastern Bulgarian city of Burgas.
"Terrorists suspected of carrying out attack," Bulgarian Foreign Minister Nikolay Mladenov told the BBC.
About 30 people were further injured when the bus exploded at Burgas airport at the Black Sea.
As per reports, the explosion took place right after a man boarded the bus. The bus was carrying tourists from a charter flight that arrived from Israel.
Israeli Prime Minister Benjamin Netanyahu later accused Iran of being behind the explosion.
"We had just sat down when after a few seconds we heard a really loud explosion," Gal Malka, one of the surviving bus passengers said. "The whole bus went up in flames."
"I saw three buses completely burnt out - just the metal bars were left," Bulgarian journalist Dobromir Dovkacharov, who arrived at the scene about 30 minutes after the blast said.
Israeli foreign ministry said: "There are six bodies on the scene - one critically wounded died at the hospital and two seriously injured are in intensive care. Thirty more people are being treated."
Wednesday's blast came on the 18th anniversary of a deadly attack on a Jewish community centre in Argentina. Israel blamed Iran for that attack - a claim denied by Tehran.
U.S. President Barack Obama described the bombing as a "barbaric terrorist attack."
"There were crowds of people around, very distressed. One man said he saw decapitated heads. Others spoke of body parts flying through the air," Mr Dovkacharov said.
Burgas airport has now been closed for the time being and flights are being diverted to Varna.
Though Bulgaria is a popular tourist destination for Israelis, there were reports early this year that Israel had asked Bulgaria to tighten security for Israeli tourists travelling by bus.
This followed by the latest discovery of a suspicious package found on a bus with Israeli tourists travelling from Turkey to Bulgaria.
The general notion is that Israeli tourists all over the world are being targeted.
This article is copyrighted by Travelers Today, the travel news leader
