The report by UN chief investigator Serge Brammertz declined to go into specific details, citing concerns for the security of key witnesses and the integrity of the probe as a whole.
The main area of progress was in establishing precisely how the massive bomb blast on the Beirut seafront in February 2005, that killed Hariri and 22 others, was carried out.
“The Commission is closer to a more complete understanding of how the preparatory work was undertaken, how those who participated on the day performed their respective tasks … and of the overall modus operandi employed,” it said.
Particular efforts were being made to use DNA tests to identify the only one of the 22 other victims who has yet to be named. The report says he might be one of the perpetrators.
Crucial progress was also reported in overcoming Syria’s initial reluctance to cooperate with the investigation.
The report said that Damascus had provided responses on a number of specific issues raised by the commission which had examined the archives of Syrian military intelligence and reviewed records related to the political situation in Lebanon as requested.
“Despite these encouraging steps, it is important to note that the
Commission will ultimately judge cooperation of the Syrian authorities on the merits of the information provided and the promptness with which its requests are being accommodated,” it added.
The report given to UN Security Council members on Tuesday, was the first by Mr Brammertz since he took up his new duties on January 23, succeeding the previous head on the commission, German prosecutor Detlev Mehlis.
Two previous Commission reports under Mr Mehlis had suggested top-level Syrian involvement in the assassination plot.
They also strongly criticised Damascus for not only failing to cooperate but also actively seeking to mislead the investigation.
Syria, the longtime powerbroker in Lebanon, has denied any involvement in Hariri’s murder and accused the UN panel of political bias.