Funerals of the five holidaymakers killed in Wednesday's suicide bombing on the Black Sea coast were held across Israel yesterday as Bulgaria's Prime Minister said he hoped the perpetrator would be identified in three or four days.

Bulgarian investigators say they have obtained DNA samples from the fingers of the bomber, who they say is not a Bulgarian national, and are working with foreign intelligence agencies in the hope of identifying the bomber.

Sweden's security services have denied Bulgarian media reports which named Stockholm-born Mehdi Ghazali, who was released from Guantanamo Bay prison camp in 2004, as the bomber.

The New York Times yesterday quoted unnamed US officials as agreeing with Israel that the bombing was the work of the Lebanese militant group Hezbollah under "broad guidance" of Iran. Israel believes that outside Lebanon, Hezbollah acts as an Iranian "proxy." The paper said the US intelligence assessment of the bombing of a bus in the resort of Burgas was that it had been a "tit for tat" reprisal for assassinations of Iranian nuclear scientists. Israel, accused with the US of the assassinations, has not confirmed or denied its involvement.

The Bulgarian interior minister, Tsvetan Tsvetanov, said the bomber might have had an accomplice, but again declined to accuse Hezbollah. The Bulgarian bus driver was also killed in the attack.

Israel yesterday sharply dismissed denials by Iranian officials of involvement in terrorism, saying that there have been 20 attacks, attempted or executed, with Iranian involvement since May 2011.

Mark Regev, spokesman for Israeli prime minister Benjamin Netanyahu, said: "The Iranian denials of their involvement in terrorism are ludicrous in the extreme and do not stand up to elementary fact-checking."

His assertion was echoed in a New York Police Department intelligence analysis reported yesterday by Reuters which said Iranian Revolutionary Guards or Hezbollah had been involved in nine plots against Jewish or Israeli targets across the world this year.

The analysis said that while Iran had sharply increased "its willingness to conduct terrorist attacks", more recent attempts had not matched the technical sophistication of earlier ones attributed to Iran.

Bulgarian prosecutor Kalina Chapkanova said that a man believed to be the bomber had tried to rent a car in Pomorie, near Burgas, days before the attack, but was refused because the picture on his driving licence showed a man with long hair while the would-be customer's was short.