A brazen daytime bombing that killed seven people and injured dozens on a bus full of Israeli tourists was most likely a suicide attack, Bulgaria's interior minister says.
He said the suspected attacker was carrying US identification documents, including a Michigan driver's licence, that was being sent to the FBI for authentication.
Tsvetan Tsvetanov said the suspected bomber appeared on security camera tape for nearly an hour before the Wednesday attack, which gutted the bus at the airport in the quiet Black Sea resort city of Burgas, about 400 kilometres east of the capital, Sofia.
According to news website novinite.com, security cameras filmed a long-haired man in sports attire idling about the location.
His body was found after the explosion.
It suffered the worst injuries and the US identification documents he was carrying were believed to be fake, leading authorities to conclude he was the suicide bomber, the website said without citing sources for the information.
The death toll stands at seven, including the suspected bomber, Tsvetanov said.
"There were seven killed... five Israeli citizens, the Bulgarian driver and the suicide bomber," Tsvetanov told a news conference a day after the blast at Burgas airport on the Black Sea.
The Israelis had just arrived on a charter flight from Tel Aviv carrying 154 people, including eight children.
No group had immediately claimed responsibility, but Israeli officials said suspicion fell upon Iran and its Lebanese proxy, the Hezbollah guerrilla group.
Iran's state TV rejected accusations of Tehran's involvement.
A commentary on Thursday on the TV website calls claims by Israeli Prime Minister Benjamin Netanyahu and others "ridiculous" and "sensational".
"All signs point to Iran," Netanyahu said on Wednesday.
"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 charges.
An Israeli military plane was preparing to fly back 30 wounded Israelis who had been hospitalised in Burgas.
Israeli Foreign Ministry spokesman Paul Hirschson said all of the wounded had left the hospital for the airport, some of them on stretchers.
Israeli doctors were to examine two more seriously wounded Israelis to see if their conditions allowed them to fly back to Israel as well, military doctor David Dagan told Army Radio.
A Bulgarian government plane will fly some 100 Israelis who were not wounded and wanted to cut short their vacation back to Israel.