Rafiq al-Hariri was killed by a truck bomb in Beirut on 14 February in an attack that Detlev Mehlis, the German prosecutor who headed a UN probe into the assassination, said involved Syrian intelligence officials and their Lebanese allies.
Saad al-Hariri, in an interview with Al Arabiya television, said: "Now they [Syria] withdrew the Syrian army, but have still kept their intelligence forces, and they're killing us ... this evil machine that is killing the Lebanese will turn against them."
The assassination of al-Hariri, a strong opponent of the Syrian domination of Lebanon, stirred an international outcry and weeks of street protests that brought about the withdrawal of Syrian forces.
Damascus sent troops into Lebanon in 1976 to try to stop a civil war.
Saad al-Hariri, a member of parliament and Rafiq's political heir, said a war was being waged against "the Lebanese democratic process".
"Do you want me to be prime minister and live what Rafiq al-Hariri lived through with Emile Lahoud? I won't do that," he said. "If President Emile Lahoud has the interests of Lebanon in mind, then he should leave his post and let Lebanon elect a new president."
A truck bomb killed Rafiq al-Hariri
in Beirut on 14 February
Al-Hariri said he had warned Lebanese anti-Syrian journalist and lawmaker Gebran Tueni not to return to Beirut, where he was killed by a car bomb earlier this month. "I used to always tell Gebran, don't go to Beirut because you are really threatened," al-Hariri said.
Tueni's was the third political killing since Rafiq al-Hariri was killed, and has caused serious political rifts in Lebanon, bringing the government to the verge of collapse.
Al-Hariri called for the establishment of an international court to try people accused of killing Lebanese politicians.
"We want anyone who kills a politician in Lebanon to know that his end will be in an international court because these people are criminals and they have to end in jail..."