Suicide bomber carried US passport The suicide bomber who killed six people including five Israeli tourists in the Bulgarian city of Burgas on Wednesday was a long-haired man in a baseball cap, T-shirt and shorts. He carried a large backpack and was in possession of a US passport, according to Bulgarian officials. Israel on Thursday repeated its claims that Hizbollah and its Iranian backers were behind the attack, raising the prospect of harsh retaliation. The blast killed five Israelis, the Bulgarian bus driver and a man believed to be the suicide bomber who set off the device. It also left at least 34 Israelis injured, including two tourists who were wounded seriously. Benjamin Netanyahu, the Israeli prime minister, blamed the attack directly on Hizbollah, describing the group as the "long arm" of Iran. "We will pursue the attackers and extract a heavy price from those who sent them," he said. We will continue fighting Iranian terror, we will act against it with great force. "For over a year, Iran, along with its protégé Hizbollah, has been waging an international terror campaign," he added, describing Iran as "the world's number one exporter of terror." Along with other senior Israeli leaders, the prime minister warned that Israel would strike back at the perpetrators of the attack, raising the prospect of a renewed outbreak of hostilities between Israel and Hizbollah. The two sides fought a 34-day war in 2006, but have since sought to maintain calm on the Israeli-Lebanese border. However, Mr Netanyahu said on Thursday: "We will continue to chase after the culprits and exact a heavy price from them. Israel is a strong country. Both Hizbollah and Iranian officials denied any involvement in the attack. The foreign ministry in Tehran issued a statement on Thursday saying that "endangering innocent lives is . . . an inhumane act and we strongly condemn it." Iran's state TV called the claims "ridiculous" and "sensational." In Berlin, Guido Westerwelle, Germany's foreign minister, urged the Israelis to show restraint until "the real perpetrators and backers" had been proven and found. Bulgarian officials revealed more details about the perpetrator, who they said was carrying a US passport and fake Michigan driver's licence. Bulgarian television broadcast security camera footage showing the suspect at Burgas airport shortly before the blast. It showed a long-haired man dressed as a holidaymaker and carrying a large backpack with wheels. Tsvetan Tsvetanov, Bulgaria's interior minister, said the authorities had obtained DNA samples and fingerprints of the suicide bomber in an effort to establish his identity. He said it had not yet been established where he entered EU territory. According to the minister, the suicide bomber had explosives in his backpack and set the device off while standing at the bus's door. Investigators were also able to find the alleged attacker's identification papers, though an FBI database check failed to turn up an individual who would match the documents. It remains unclear how he obtained the fake passport, and how and when he entered the country. ABC showed a picture of the driver's licence, according to which the presumed bomber impersonated Jacque Felipe Martin of Baton Rouge, Louisiana. Bulgarian authorities are still examining whether the alleged attacker's US passport is forged as well.