The 14 February 2005 killing of al-Hariri turned the political landscape on its head in Lebanon, with large protests forcing Syria to end its three decades-old military presence and a general election sweeping to power an anti-Syrian coalition for the first time since the end of the 1975-1990 civil war.
Hundreds of thousands of people packed into central Beirut on Tuesday, waving red and white flags and pictures of the slain prime minister who was credited with rebuilding the country after the devastating civil war.
Arriving at Freedom Square by bus, car or on foot, demonstrators chanted "No, no to the mukhabarat" in reference to the once-feared Syrian secret police, as loudspeakers played patriotic songs and Quranic verses.
The rally was called by the anti-Syrian coalition led by al-Hariri's son and political heir, Saad al-Hariri, who says that those behind the killing should be brought to justice.
Rafiq al-Hariri and 22 others died
in a car-bomb blast
Demonstrators carried pictures of other Lebanese politicians and journalists targeted in bombings over the past year.
The city centre was closed to traffic against a background of a massive security deployment for the anniversary.
Saad al-Hariri had returned home at the weekend after six months in exile to issue an appeal for a massive turnout.
Al-Hariri, the head of the anti-Syrian majority in parliament, said: "I call on all Lebanese to adopt a historic position of unity on this day to show that our national unity is above all else and that the forces of 14 March will remain united."
Al-Hariri said in an interview with Lebanese television: "We do not ask for a change of regime in Syria, but that it makes peace. We thank Syria for having ended the war in Lebanon but we will handle our own affairs now.
"The Syrian regime did a lot of wrong in Lebanon and spared her neither insults nor threats."
However, in a sign of continuing divisions in Lebanon, the pro-Syrian Shia movement Hizb Allah and a major Christian leader, former general Michel Aoun, have refused to endorse the commemoration, saying it had been "politicised".
Jumblatt: Every Lebanese is
invited to pay homage to al-Hariri
Rafiq al-Hariri was buried in a mosque that he built on Martyrs' Square, popularly renamed Freedom Square after his death.
"Every Lebanese is invited to pay homage to Rafiq al-Hariri on Tuesday by placing a rose at the site of the attack or at his tomb," said Walid Jumblatt, a Druze leader and anti-Syrian member of parliament.
The rally in Freedom Square, described as a "gathering of loyalty and national unity", climaxed shortly after midday, the time when a huge truck bomb exploded on a downtown seaside street as al-Hariri's motorcade drove by, killing him and 22 others.
Security measures were tightened after a demonstration against cartoons depicting Prophet Muhammad turned into a riot in which the Danish mission was torched and a church vandalised.
A Beirut billboard carrying the
picture of the slain ex-premier
"We miss you," read large posters with a smiling al-Hariri.
"They feared you, so they killed you," others said.
Many in Lebanon say Syria was behind the killing of al-Hariri.
An ongoing UN inquiry has implicated senior Syrian security officials and their Lebanese allies.
Damascus denies any role.