Nabih Berri, the pro-Syrian parliamentary speaker, whose Amal group is an ally of fellow Shia movement of Hezbollah, told As-Safir newspaper that the street protests would continue, but urged calm.
And Christian leader Michel Aoun said that the Lebanese opposition would escalate its protests if the government failed to accept demands for a national unity cabinet.
"If the prime minister and his camp continue to monopolise power, there will be an escalation of popular pressure," Aoun told Associated French Press. "We will paralyse the government ... we will force it to go into a deep coma."
The Organisation 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".
Lebanon's Maronite church also weighed in, urging an early presidential election, an tribunal into the killing of Rafiq al-Hariri, and the formation of a new "government of accord" to end the political deadlock.
The opposition, made up of Shia and Christian factions, has held demonstrations since Friday outside the offices of Fouad Siniora, the Lebanese prime minister,in central Beirut where he and several ministers have been holed up.
Accusations of meddling
In a speech in Damascus, Faruq al-Shara, the Syrian vice president, said on Wednesday that he criticised the stream of visits to Beirut by Western officials and accused them of meddling in Lebanon's domestic affairs.
"This interference aims to place the country under foreign hegemony so as to separate it completely from Syria," Shara said, quoted by the official Syrian news agency, SANA.
"The endless visits by western officials dictating their will on Lebanon ... amounts to interference," he said.
Al-Shara also stressed Syria had "no intention of returning militarily to Lebanon having decided to close that file definitively", since its 2005 troop pullout.
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.