BEIRUT, Lebanon - The head of a United Nations probe into the assassination of former Lebanese premier Rafik Hariri has secretly visited Damascus several times in recent months to question top Syrian officials implicated in the February 2005 attack, a Qatari newspaper reported Wednesday.

During one or more of these trips, Belgian magistrate, Serge Brammertz, who heads the UN commission of inquiry, interrogated the former chief of Syria's security services in Lebanon, Rustum Ghazale, the daily ash-Sharq, said citing an unidentified source in Damascus.

The commission has linked Ghazale to the Beirut carbomb blast that killed Hariri and 22 others.

The source who was described in the report as "well placed," within the Syrian government also told the daily that no proof exists of any involvment by Syria in the attack.

To date only two visits by Brammertz to Damascus have been officially announced, a trip in February when the commission chief met Syrian foreign minister Walid al-Muallim and the government's top legal afairs aide Riyad Dawudi, and another visit in April when Brammertz met Syrian president Bashar al-Assad and his deputy, Faruq ash-Sharaa.

Brammertz is scheduled to submit a report of his findings ocer the last six months to the United Nations on 15 June.

Brammertz's predecessor, German magistrate Detlev Mehlis, said in his tow reports to the UN that "convergent proof" existed of a role played by the Syrian and Lebanese security services in the 14 February 2005 bombing.

While Mehlis questioned Damascus' willingness to cooperate with the investigation, Brammertz in his March report said that Syria had "made progress" in this. (AKI)