Hundreds of thousands of flag-waving Lebanese packed a square in central Beirut on Tuesday to mark the anniversary of the assassination of former Prime Minister Rafik Hariri, a momentous event that ended Syria's long domination of its smaller neighbor.

Thousands of troops and policemen, backed by armored vehicles, sealed off Beirut's downtown to bolster security. The government gave schools the day off and businesses closed to allow people to participate. Buses brought in people from the countryside.

The demonstration in Martyrs' Square next to Hariri's grave drew mostly Sunni Muslims from the former leader's sect and Christian and Druse allies; the main pro-Syrian Shiite Muslim groups, Hezbollah and Amal, were not taking part.

The participants included women in both headscarves and jeans. Some carried signs calling for "The Truth" and shouted the name of Hariri's son and political heir, Saad Hariri.

Others carried placards critical of Syria and its president, Bashar Assad. "Isn't it enough, Bashar?" said one, listing the names of anti-Syrian Lebanese who have been slain in other bombings in the last year.

"Those who killed Hariri meant to kill Lebanon, but they failed. A new united Lebanon was born," said Samia Baroudy, a 52-year-old housewife from the Christian suburb of Rabieh. Holding a Lebanese flag, she said Hariri's death was both "a disaster" and "a miracle" that brought the Lebanese together.

Mohammed al-Ali, a 24-year-old Muslim barber from the northern province of Akkar, said he came to "to affirm the country's unity and Muslim-Christian coexistence."

In France, Hariri's widow planned to lead a vigil for the former premier at a church later in the day.

Hariri was killed on Feb. 14, 2005, when a huge truck bomb exploded on a downtown Beirut street as his motorcade drove by. Twenty others were also killed.

Anti-Syrian groups were hoping Tuesday's rally would be a repeat of a March 14 protest in which about 1 million flag-waving Lebanese converged on Martyrs' Square to demand the Syrian army leave Lebanon and that an international investigation look into Hariri's slaying.

Syria's troops left in April under international pressure, and a United Nations probe into Hariri's murder has implicated top Syrian and allied Lebanese security officials. The pro-Syrian administration was also ousted from office.

But anti-Syrian groups have continued to accuse Syria of interfering in Lebanese affairs and carrying out a campaign of bombings and assassinations in the past year that has killed 11 people, including three prominent anti-Syrians. Damascus has denied involvement in the Hariri murder and other attacks.

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 civil war that lasted another 14 years. The army stayed after the war ended in 1990, controlling the country's politics and military.

Saad Hariri, the slain former premier's son and head of the largest parliamentary bloc, returned to Beirut on Sunday after months of self-exile in Saudi Arabia and France for fear of assassination. He urged the Lebanese to join him in the gathering.

"The Lebanese people must show the entire world that we reject any tutelage, any oppression and any crime," he said in a television interview with LBC TV station late Monday. "The message that must be conveyed tomorrow is that we refuse to have our independence and freedom threatened. It is a message of loyalty for all the martyrs."

The demonstration was carried live by most Lebanese television stations.

However, Syria's official media did not broadcast any live footage. "We want all the truth," headlined one front-page editorial in Al-Thawra newspaper, a reference to Syria's claim it was being unfairly accused in the murder.

Army and police checkpoints were keeping vehicles away and providing protection for the demonstrators, unlike in some protests last year when security forces tried to block the protesters. Security forces searched men and women arriving at the square, apparently fearing explosives.

The high security also was to avoid repetition of a Feb. 5 demonstration that turned into a riot outside the Danish mission in Beirut. Muslim extremists set fire to a building housing the mission to protest the publication of cartoons of the Prophet Muhammad by a Danish newspaper.

The ongoing U.N. investigation into Hariri's murder has already determined the assassination could not have been carried out without the knowledge of Syrian intelligence and Lebanese allies in the security services.

U.N. investigators have questioned top Syrian security officials, including the last Syrian intelligence chief in Lebanon, and have asked to interview Assad. A former Syrian vice president has said Assad had threatened Hariri at a meeting months before the assassination, but Assad has denied that.