Bulgarian police along with the CIA, FBI and Interpol are struggling to identify a suicide bomber who killed six people, including five Israelis, as the US said the attack bore the “hallmarks” of Hizbollah.

Investigators released CCTV footage of the person they believe carried out Wednesday’s attack at the airport of the Black Sea town of Burgas on a bus carrying Israeli holidaymakers, which also killed the Bulgarian driver.

After two days of investigations, Interior Minister Tsvetan Tsvetanov was able only to confirm on Friday that the bomber was not a Bulgarian citizen and had been in the country “not less than four days”.

Fingerprints and DNA samples from the suspected bomber’s body were being used in the effort to learn his identity, he added.

The minister also made public on Friday evening some scanty details on the explosive used in the first attack of its kind in Bulgaria. “We are speaking about trotile, about three kilos. Analyses are continuing,” he told state BNT television.

Trotile is made from Trinitrotoluene or TNT – a common material in military bombs and also frequently used in attacks by militant groups.

Bulgaria’s Pressa newspaper and the bTV channel said the bomber could have had an accomplice who detonated the explosives by cellphone.

A man and his wife who ran a car rental service said they recognised the suspect who came to hire a vehicle. They said he had a wad of €500 bills and refused to rent him a car as his US driving licence appeared to be a fake.

Burgas prosecutor Kalina Tchapkanova quoted witnesses as saying the man “spoke English with a slight accent” and appeared to be Arab.

The car rental service owner’s wife Afrodita Petrova said she was sure he was of Arab origin and had a shaved head.