Hundreds of thousands of flag-waving Lebanese, some carrying anti-Syrian banners and many shouting criticism of Damascus, massed in a square in Beirut on Tuesday to commemorate the first anniversary of former Premier Rafik Hariri's assassination.
The gathering answered a call by groups opposed to Syrian involvement in lebanon aiming to show their popular strength amid deep political divisions.
Next to the square Rafik Hariri's sister Bahia Hariri prayed at his graveside before anti-Syrian politicians addressed the crowd.
Those politicians, including Hariri's son, Saad, and cabinet ministers, called for the ouster of President Emile Lahoud, saying he represented the symbol of Syrian power in Lebanon.
Lebanon's information minister, Ghazi Aridi, said the truth about Hariri's assassination will come out:
"It will be the international tribunal and the truth will be very clear for all the Lebanese people and the international community."
Some speakers attacked Syrian President Bashar Assad.
Saad Hariri, the slain premier's son and political heir, returned to Beirut on Sunday - after months of self-exile in Saudi Arabia and France for fear of assassination, urging the Lebanese to demonstrate on Tuesday.
Thousands of troops and policemen, backed by armoured vehicles, sealed off Beirut's downtown area to provide security and guarded approaches to the Lebanese capital.
The government, which is dominated by the Saad Hariri bloc, gave schools the day off to maximise participation.
Businesses also closed.
Thousands of people began gathering by mid-morning, carrying Lebanese flags and pictures of Hariri, and the numbers had swelled to more than 700,000 by early afternoon, according to police estimates.
The demonstration, on the central Martyrs' Square next to Hariri's grave, climaxed shortly after midday local (1000gmt).
The crowds fell silent at 12:55 p.m. (1055GMT) - the time when a huge truck bomb exploded on a downtown street as Hariri's motorcade drove by a year ago, killing him and 20 others.
The groups who organised Tuesday's rally were looking for a repetition of a March 14 protest in which about one (m) million Lebanese converged on Martyrs' Square to demand the Syrian army leave Lebanon.
It fell short of that outpouring, but was still a comprehensive turnout.
Syria's troops left in April under international pressure, and a UN probe into Hariri's murder has already implicated top Syrian and allied Lebanese security officials.
Anti-Syrians have continued to accuse Syria of interfering in Lebanese affairs and carrying out a campaign of bombings and assassinations in the last year that has killed other 11 people, including three prominent anti-Syrians.
Damascus has denied involvement in all these attacks, including the death of Hariri.
Before the troop pullout, Syria had dominated Lebanon with its army and security services for nearly three decades, first entering in 1976 to quell a fratricidal civil war that did not end until 1990.