After meeting on Friday in a Beirut hotel, they urged the Lebanese people to back a peaceful "independence uprising" – using the word intifada in Arabic, the first time they had used the term.
They also called for parliament to suspend all debate unrelated to the assassination until the truth about who killed former prime minister Rafiq al-Hariri emerged.
"This isn't just the opposition," Druze leader Walid Jumblatt earlier told reporters. "All the Lebanese are with al-Hariri, a free Lebanon and [a] Syrian withdrawal."
"In response to the criminal and terrorist policy of the Lebanese and Syrian authorities, the Lebanese opposition declares the democratic and peaceful intifada [uprising] for independence," said leading opposition figure Samir Frangia after a meeting of leading Lebanese opposition figures.
"We demand the departure of the illegitimate regime," Frangia said, reading a final statement at Jumblatt's home.
Jumblatt did not attend the meeting, held four days after al-Hariri's assassination for "security reasons," aides said.
The opposition demands that
Syrian troops withdraw
They did not say what kind of protests the uprising would involve, but they did say their actions would be peaceful.
Prime Minister Umar Karami responded to the opposition's demands by saying they amounted to a "coup attempt against the state".
He also refused an international investigation into Hariri's killing.
The Lebanese opposition has changed rapidly since the assassination last Monday and there is a new political dynamic in Lebanon.
While conflict in Lebanon has traditionally occured between the different sects, now the two opposing sides consist of those who support and oppose Syria's involvement in Lebanon.
"It's different from the 1975 patterns," said Nizar Hamza, a politics professor at the American University of Beirut, in reference to the political groupings in Lebanon at the start of the 1975-1990 civil war.
"Now we are really talking about loyalists and oppositions and they are made up of different sects," he told Aljazeera.net.
The support for the opposition
has now broadened in Lebanon
While the opposition to Syria's presence in Lebanon was initially almost exclusively dominated by Christian groups, the opposition now has a wider base.
With this kind of consensus, it seems the opposition has become emboldened and views this as being the optimum time to step up its campaign to pressure Syria to withdraw the 14,000 troops it keeps in Lebanon.
However, analysts said that rash decisions at this sensitive time could result in dire consequences.
"People smell momentum. I just hope people keep their heads a little bit. There is a momentum but this involves so many issues that cannot be resolved over night," International Crisis Group analyst in Beirut Reinoud Leenders told Aljazeera.net.
"The whole prospect for sectarian conflict is very much looming over the whole situation now," he said.
"I just hope people keep their heads a little bit"
ICG analyst Reinoud Leenders
Leenders warned that the Syrian government might seek to dig its heels in if it was under too much pressure to leave Lebanon.
"You can push Syria and at some level if will start to look for different avenues and at some point you can push too much and they can decide to bring the whole house down," he said.
Leenders said that Syria could seek to stir trouble in Lebanon by provoking conflict, perhaps between the 300,000 Palestinian refugees who reside in Lebanon and the Lebanese state.
Rime Allaf, Middle East analyst from the Royal Institute for International Affairs, questioned how long the apparent unity between the different groupings in the opposition would last.
"What agenda do they actually have? Do they have agreements on all the other issues in Lebanon? They are riding on the wave that came after al-Hariri's assassination."
Allaf questioned whether the different factions had anything in common apart from a desire to see the Syrians leave Lebanon.
"Have they got an agreement on what will happen to the Palestinian refugees? Have they got an agreement on what will happen with Hizb Allah?" she asked.
Hamza said that while the opposition appeared to be taking on a broader sectarian base, it was really too early to predict what would happen in the long term.
"In [the message of] Friday's prayers of Sunni shaikhs it didn't seem that the Sunni traditional alliance had moved to the alliance of the opposition. The coming two weeks will give final answer for that," he said.