Ban said last week he expected the international tribunal that will prosecute suspects in the assassination to begin operating March 1.

Political violence

Al-Hariri's killing was one of the most devastating acts of political violence to hit Lebanon since the 1975-1990 civil war, and led to the withdrawal of Syrian troops after a 29-year presence.

Al-Hariri, a wealthy businessman opposed to Syria's interference in Lebanese affairs, died after a massive explosion destroyed his armoured car on Beirut's seafront on February 14, 2005, along with twenty-two other people.

Investigators have said a likely motive for the killing was the role of al-Hariri in support of a 2004 UN resolution demanding that Syrian and other foreign troops withdraw from Lebanon.

Nobody has been charged, though four pro-Syrian Lebanese generals have been under arrest for three years for alleged involvement in the murders.

The investigation

An independent team of investigators, headed by Canadian prosecutor, Daniel Bellemare, has been helping Lebanese authorities investigate 20 other bombings and assassinations in Lebanon since October 2004, and there are "links between those cases and the Hariri case", Ban said.
  
The original head of the UN investigation, Detlev Mehlis, implicated senior Syrian officials in the case, but his two successors, including Bellemare, have not repeated the charge and no suspects have been publicly identified.

Investigators collected additional soil, sand and water samples from states in the region and used radioactive isotopes to try to determine where the bomber came from.
   
"The results of these activities help to identify the possible geographic origin of the suicide bomber," Bellemare said, without elaborating.
   
Bellemare, who will also be the chief prosecutor in the case, played down expectations that the start-up of the tribunal in The Hague would mean that indictments naming alleged perpetrators would be issued immediately.
   
Further investigations would be needed, he said.