Bellemare, who took over from Belgium's Serge Brammertz at the beginning of 2008, said he was aware that many people would like the investigation to move more swiftly but said that it would take time before any indictments were issued.
In his first report to the Security Council on March 28th, Bellemare said investigators have evidence that Hariri was assassinated by a "criminal network" linked to some other terrorist attacks in Lebanon.
The eleven attacks highlighted by the Canadian prosecutor have targeted politicians, journalists and security officials, mostly in public places, killing a total of 61 people and injuring almost 500 others.
Bellemare said he was following Brammertz "in terms of investigating crimes that are politically motivated".
In July, Brammertz said that investigators believed the September 2004 Security Council resolution aimed at blocking Emile Lahoud, Lebanon's president, from a second term in office "played an important role in shaping the environment in which the motives to assassinate Rafiq Hariri emerged".
Brammertz also said that Hariri's prominent role as a critic of Syria, in support of the UN resolution, made him a target.
Syria denies any involvement in Hariri's assassination, but the international outrage over the attack forced Syrian troops to withdraw from Lebanon after a 29-year presence.
Bellemare says investigation is incomplete and
needs six more months to complete it [EPA]
Four Lebanese generals have been under arrest for almost two years for alleged involvement in Hariri's murder.
On Tuesday, Bellemare was asked by Russia about the generals' continued detention without charges.
He said their detention is the result of a decision by Lebanese judicial authorities "pursuant to Lebanese criminal law".
Bellemare said his panel's priority was now to gather more evidence about what he called the "Hariri network", its scope, the identity of all its participants, their links with others outside the network and their role in the attacks.
"The direction of the investigation has not changed and the commission is still investigating crimes that are politically motivated," he said.
"What is new this time is that we now have the evidence of the existence of such a network and of its links," he added.
Bellemare is to become the special tribunal's prosecutor once the UN probe of the Hariri and related cases is completed.