BEIRUT, Lebanon - Hundreds of thousands of Lebanese opposition supporters, led by the Shiite militant group Hezbollah, gathered Sunday in the central district of Beirut to take part in a mass rally to exert pressure on the anti-Syrian government to resign.

The demonstration comes on the 10th day of a sit-in outside the offices of Prime Minister Fouad Seniora.

The Hezbollah-run al-Manar television station described the rally as a 'historic one which Lebanon has not witnessed before.'

Organizers estimated the crowd to be more than 1 million, but police on the ground questioned the figure, saying the two squares where the demonstration took place could not hold so many people especially as tents had been set up there.

Most of the roads leading to the squares were blocked to traffic.

'Death to America, death to Israel,' Hezbollah's deputy chief Sheikh Naeem Kassem shouted to the protestors, many of whom were waving Lebanese flags.

Kassem called on Seniora to resign 'either tonight or tomorrow' and stressed that the protests would continue and that the protestors would 'not be tired.'

He accused the government of taking 'Lebanon towards the American hegemony.'

The protestors say Seniora's government does not represent them and it is 'unconstitutional' after six pro-Syrian ministers resigned last month.

Speaking to the protestors via a large screen, Hezbollah's Christian ally and hardliner General Michel Aoun called for patience because there would be an escalation of the protests in the coming days.

'All means are legal,' Aoun said. He gave examples like Ukraine and other places in eastern Europe where protestors stormed parliament and governmental offices.

Aoun threatened to form an interim government which would take Lebanon to an early parliamentary elections.

He accused the government of corruption and said the opposition would soon take control of all of the government and not only a third as they currently did.

Despite the mass rally which started at 1300 GMT, Seniora addressed a crowd of his anti-Syrian followers commemorating the passage of one year since the assassination of member of parliament and journalist Jubran Tueini.

'I tell the world and our Arab brothers that the Lebanese are strong people and they will manage a way out of this crisis,' Seniora said.

Tueini, a staunch critic of the Syrian regime, was assassinated in a car-bomb blast on December 12, 2005.

Opposition sources told Deutsche Presse-Agentur dpa that demonstrators might escalate their action to paralyse main roads, including the Beirut airport road.

But government sources have 'warned against any dangerous escalation that may paralyse the country and its economy, and which may trigger an even more dangerous counter-escalation.'

Supporters of the government, led by the anti-Syrian parliamentary majority, have also been staging large rallies in various areas across Lebanon and also organizing daily visits to Seniora's offices to express their solidarity.

The protests started on December 1.

The tense situation has prompted Arab leaders like Saudi Arabia's King Abdullah bin Abdul Aziz al-Saud to issue warnings.

'In Lebanon, we see dark clouds threatening the unity of the homeland, which risks sliding again into ... conflict among the sons of the same country,' Abdullah said at the opening of the annual summit of Gulf leaders on Saturday.

Meanwhile, the protest continued. 'We are here today to show Seniora that we are the majority along with our Christian brothers,' a follower of Hezbollah said Sunday.

'There will be lots of surprises in today's rally,' the follower added without elaborating.

Some of Aoun's followers were dressed in their party's orange, but in Santa Claus outfits complete with ringing bells.

'We are here to say with our Muslim brothers we do not want the Seniora government any more,' one of Aoun's Santas said.

Meanwhile, in church services across Beirut, priests called for an end to the street protests to allow the Lebanese to celebrate the upcoming Christian holiday.

The head of the Greek Orthodox community in Lebanon, Archbishop Elias Audi, said that 'everybody has the right to celebrate their feasts in peace.'

'We are approaching a major Christian feast and we want them (the opposition) to allow the people to celebrate it in peace and harmony,' Audi said.

The head of the Maronite Christian church Cardinal Nasrallah Sfeir, called on all Lebanese leaders to sit together and spare the Lebanese from economic hardships.

The opposition are accusing the government of corruption and taking orders from the US administration; the government is accusing the opposition of getting its orders from Syria and Iran.

The opposition wants to stop the establishment of an international tribunal to try suspects in the 2005 assassination of former premier Rafik Hariri, the government says.

'Their masks are off now ... they are protecting the killers of Hariri by these protests,' a follower of Hariri said.

Seniora has described the demonstration as an attempted 'coup' by the Tehran- and Damascus-backed Hezbollah to return Syria's influence to the country.

After Hariri was killed and due to international and local pressure, Syria withdrew its military from its smaller neighbour after a 30-year presence on April 26, 2005.

An ongoing UN probe has implicated Syrian officials and their Lebanese allies in the Hariri assassination. Damascus has vehemently denied such charges. -DPA