Bulgaria said Thursday a suicide bomber dressed as a tourist and with fake US ID was behind an attack on Israelis on the Black Sea that killed seven people and left two in a coma.

US President Barack Obama called the attack on a bus at Burgas airport on Wednesday, the deadliest against Israelis abroad since 2004, a "barbaric terrorist attack" as Israel blamed Iran and Lebanese Shiite group Hezbollah.

"The suicide bomber, wearing shorts and carrying a backpack, looked like any other tourist," Bulgarian Interior Minister Tsvetan Tsvetanov said.

"He put his bag in the luggage compartment of the bus that blew up," he told reporters.

"His travel document was a fake driving licence from the (US) state of Michigan ... (His) identity has not yet been established."

The explosion ripped through the bus as around 50 Israeli tourists who had just arrived by charter plane from Tel Aviv were loading their bags and boarding a bus about to take them to a nearby seaside holiday resort.

Five of the tourists died at the scene while a sixth, and the vehicle's Bulgarian driver, died from their injuries in hospital. The bomber also perished. Around 30 people were injured.

Witnesses described how panicked passengers jumped from bus windows and bodies lay strewn on the ground with their clothes torn off as ambulance sirens wailed and black smoke rose over the airport.

"I was on the bus and we had just sat down when after a few seconds we heard a really loud explosion," one Israeli tourist, Gal Malka, told Israeli army radio. "The whole bus went up in flames."

"We are facing a global wave of terror... the attack in Burgas was led by members of Hezbollah and sponsored by Iran," Israeli Defence Minister Ehud Barak told public radio.

"The Al-Qaeda and Islamic Jihad networks also operate globally," he added, citing a long list of recent attacks or attempted attacks on Israelis around the world including in Thailand, India, Georgia, Kenya and Cyprus.

"These attacks against innocent civilians, including children, are completely outrageous," said Obama, who expressed his condolences in a phone call with Israeli Prime Minister Benjamin Netanyahu.

"The United States will stand with our allies, and provide whatever assistance is necessary to identify and bring to justice the perpetrators of this attack."

The bombing, which came on the 18th anniversary of an attack on a Jewish community centre in Argentina that killed 85 people, also drew strong condemnation from France, Britain, Russia and others.

"Moscow resolutely condemns this new criminal foray by terrorists, which sought to kill innocent civilians who included women and children," the Russian foreign ministry said in a statement.

French President Francois Hollande expressed his "indignation" at what he called a "barbaric act."

US Secretary of State Hillary Clinton, who visited Israel on Monday and held talks with Netanyahu on the last stop of a nine-nation tour, said she was deeply saddened and angered to learn of the attack.

Except for two people in a coma transferred to the capital Sofia, the other injured were taken to to Burgas airport on Thursday morning amid a heavy police presence, to be flown home to Israel, an AFP reporter at the scene said.

They included a pregnant woman and a girl of around seven or eight years old who was carrying her flip-flop because her right foot was wrapped in bandages.

Around half of the injured were teenagers. Many of those hurt were brought out to the ambulances in wheelchairs with many having sustained burns and tear wounds on their legs and arms.

Others limped to the ambulances on their own -- some blood-stained, barefoot, clutching shoes and other scanty personal belongings they had on them when the explosion hit. They refused to talk to reporters, with many talking on phones.

"They will be transported by airplane to Israel," said Uri Shacham, an assistant to the director-general of the Magen David Adom, the Israeli equivalent of the Red Cross.

Around 20 Israeli paramedics arrived overnight to help treat the wounded. Apart from the flight back to Israel, Burgas airport remained closed on Thursday morning.

Israel and former communist Bulgaria, which has a 13-percent Muslim population, enjoy good relations and the Black Sea coast has become a popular holiday spot for Israelis, with almost 140,000 visiting the country in 2011.

In January, Israeli public television reported that authorities in European Union member Bulgaria had foiled a bomb attack when they found an explosive device on a bus chartered to take Israeli tourists to a ski resort.

Bulgarian troops were deployed in several ski resorts frequented by Israeli tourists after the bomb was found, the report added.