BEIRUT, Lebanon - Thousands of demonstrators, many camped out in a tent city in Beirut, staged a sixth day of protests as the opposition vowed to step up its campaign to topple Lebanon's Western-backed government.

The opposition called for a new massive demonstration on Sunday and asked the Lebanese people to prepare for other forms of peaceful protest to force the formation of a new unity government.

"We call on the Lebanese to participate en masse in a demonstration Sunday in central Beirut at 3 pm (1300 GMT) in the hope that this will be a historic day on which our voices are heard," the opposition said in a statement.

It also asked the Lebanese to "be ready for other forms and means of peaceful protest" to obtain the fall of the government, which is backed by an anti-Syrian parliament majority elected in 2005.

It did not elaborate.

Earlier, influential pro-Syrian parliamentary speaker Nabih Berri, whose Amal group is an ally of fellow Shiite movement Hezbollah, told As-Safir newspaper that the street protests would continue, but urged calm.

And Christian leader Michel Aoun warned that the Lebanese opposition, led by the Syrian-backed Hezbollah, would escalate its street protests if the government failed to accept demands for a national unity cabinet.

"If the prime minister and his camp continue to monopolize power, there will be an escalation of popular pressure," Aoun told AFP in an interview. "We will paralyze the government, we will force it to go into a deep coma."

Deep political tensions in Lebanon and a number of street fights that have killed at least one Shiite sympathizer have raised concerns of a resurgence of sectarian strife in a country still reeling from the 1975-1990 civil war.

The opposition, made up of Shiite and Christian factions, has held demonstrations since Friday outside Prime Minister Fuad Siniora's offices in central Beirut where he and several ministers have been holed up.

The opposition is seeking a greater say in the Siniora government, which is hanging by a thread after six pro-Damascus ministers quit.

Siniora's coalition has accused the opposition of seeking to block a cabinet decision for an international tribunal to try suspects in the 2005 murder of former premier Rafiq Hariri, widely blamed on Syria.

Amid tension on the streets, Berri appealed for calm and warned that "if some have not learned from past discords in Lebanon and want to take back the country to what it was 16 years ago, let them (bear the responsibility)."

Lebanon's Maronite church also weighed in, urging an early presidential election, a Hariri tribunal, and the formation of a new "government of accord" to end the political deadlock.

The Organization of the Islamic Conference urged Lebanese leaders to act with "the highest degree of self-restraint, wisdom and responsibility in order to save the country from slipping on the inevitable slope of confrontation."

Arab diplomats, fearful of a return to civil strife, are attempting to mediate the crisis, while Western governments have expressed support for Siniora and his government.

Arab League chief Amr Mussa, who was in Beirut at the weekend, said Tuesday there was a "glimmer of hope" that the crisis might be defused and said he had presented ideas on the government and an international donor conference to help Lebanon's struggling economy.

The conference to be held in Paris next month aims to secure long-term assistance to help Lebanon recover from last summer's Israel-Hezbollah war which caused more than 3.5 billion dollars in damage.

Turkish Prime Minister Recep Tayyip Erdogan held talks with Syrian President Bashar al-Assad in Damascus on Wednesday focused on efforts to ease tensions in neighbouring Lebanon and Iraq as well as on the Israeli-Palestinian front.

Germany and France have issued a joint call for Syria to "stop supporting forces that seek to destabilise Lebanon and the region," after Damascus threw its weight behind the opposition earlier this week. -AFP