Tens of thousands of Lebanese opposition supporters on Sunday demanded Hezbollah be disarmed as they rallied to mark the sixth anniversary of a popular uprising against Syrian troops in the country.

"It is impossible that any of us here accept tutelage over Lebanon again, whether foreign domination or the domination of arms within Lebanon working for foreign interests," said outgoing prime minister Saad Hariri, in reference to the arsenal of the Iranian-backed Shiite militant group.

"It is impossible to accept that these weapons ... continue to be turned against the democratic will of the people," said Western-backed Hariri, son of ex-premier Rafiq Hariri whose 2005 assassination sparked the uprising that led to the departure of the Syrians.

A massive crowd thronged Martyrs' Square in central Beirut, focal point of the protests six years ago, waving the national flag and the banners of pro-Western political parties.

"The people want the fall of arms," the demonstrators chanted amid tight security.

"We are here to say yes to life and no to their arms," said Adnan Antar, 65, who travelled from the northern port city of Tripoli to attend the rally with his family along roads clogged with convoys blaring songs and displaying pictures of Rafiq Hariri.

"There can be no rule of the state in Lebanon as long as there is the rule of arms," he added.

Hariri's assassination in a February 14, 2005 Beirut bombing saw the rise of a US- and Saudi-backed alliance that became known as March 14, named after a day of massive anti-Syrian protests dubbed the "Cedar Revolution."

Combined with international pressure, the protests in the weeks after the killing led to the pullout of Syrian troops from Lebanon in April 2005, ending 29 years of military and political domination by Damascus.

The rally this year comes as Hezbollah's military might is once again the focus of a deadlock between rival Lebanese camps.

"We will not accept that the Lebanese economy continue to be paralysed... nor that our history be distorted," Christian leader Samir Geagea, head of the Lebanese Forces party, said at the rally.

"We say no to the exploitation of Lebanon for the benefit of Iran," Hezbollah's main backer, said Geagea.

Several demonstrators carried banners reading "NO to the dictatorship of arms" and "God has no arms," in reference to Hezbollah, Arabic for "Party of God."

"We will not stand by as witnesses who fear their reaction which could turn violent," said Salim Eid, 46, a supporter of the Christian Lebanese Forces party.

"Let's hope they don't have a violent reaction to this rally here today."

The anniversary comes amid a drawn-out political crisis which saw Hezbollah topple Saad Hariri's unity government in January, capping a long-running feud over a UN-backed Special Tribunal for Lebanon.

The tribunal -- tasked with investigating the Rafiq Hariri murder -- is reportedly readying to implicate members of Hezbollah in the killing.

Sunni Muslim billionaire Najib Mikati, appointed with Hezbollah's backing, has been tapped to succeed Saad Hariri and has since January 25 sought to form a government.

The Hariri-led opposition has announced it will boycott Mikati's government, which it accuses of being "Hezbollah's cabinet".

Lebanon's opposition has accused Hezbollah, the only party not to have turned in its arms after the 1975-1990 civil war, of having used its arsenal to intimidate MPs into voting against Hariri's re-appointment after his unity cabinet collapsed.

The March 14 camp also accuses Hezbollah of using its arms during the events of May 2008, when a protracted political crisis culminated in a week of street clashes that killed 100 people