Beirut, Jan 17 (Agencies): Lebanon's caretaker Prime Minister Saad Hariri informed a UN Commission Syria was behind his father's killing, according to a leaked recording of a 2007 meeting between Hariri and an investigator probing the case.

In the audio-tape, aired late Sunday on Lebanese television and authenticated by Hariri's office, the acting premier singled out a string of Syrian officials he held responsible for the 2005 bombing that killed his father, ex-premier Rafiq Hariri, and 22 others.

The leak also featured the normally reserved Hariri openly accusing Syrian leaders of blackmailing his father and slamming President Bashar al-Assad as an "idiot".

In the recording, Hariri tells investigator Lajmi Mohammad Ali in a meeting on July 30, 2007 that Syrian Foreign Minister Walid Muallem warned his father he was "walking on dangerous ground" weeks before his death.

"If you ask me how it (the assassination) happened and why it happened, I think that Assef Shawkat and Maher (al-Assad) had a huge role in the preparation ... in pushing (Syrian President) Bashar (al-Assad) to take that decision," Hariri said in English.

Shawkat, Assad's brother-in-law, is Syria's military intelligence chief. Maher al-Assad is the brother of the Syrian president and former head of the presidential guard.

The tape was aired by New TV, which is close to Hezbollah, on the eve of indictments set to be submitted by the prosecutor of the Netherlands-based Special Tribunal for Lebanon (STL), which is investigating Hariri's murder.

The powerful Shiite militant group has said it believes some of its members will be implicated in the killing and has warned it will defend itself.

Hariri, whose office issued a statement apologising to several local figures he criticised in the recording, had especially harsh words for Assad, whom he has sought to move closer to over the past year.

"You know Bashar became president when he was 34 and ... went to the first Arab summit ... and he gave a lecture to kings and presidents who have been there for the past 15 years," said Hariri, who was not premier at the time of the interview. "And it struck me: you idiot, the least you could do is not give a lecture about Arabism."

Hariri also accused Syrian intelligence official Rustum Ghazali of blackmail, saying he regularly took as much as USD 90,000 in cash from his father and requested other services.

Ghazali was head of Syrian military intelligence in Lebanon from 2002 until 2005, when Damascus pulled its troops from its smaller neighbour after a 29-year deployment.