Lebanon's opposition has called for a peaceful "independence uprising" and said the government should step down.
Mourners of all faiths have been paying their respects to Hariri
The opposition holds both the Lebanese and Syrian governments responsible for the assassination on Monday of former Lebanese Prime Minister Rafik Hariri.
Hariri's death in an explosion in Beirut has sparked anti-Syrian feeling.
Tourism Minister Farid al-Khazen resigned on Friday, saying the government was unable to "remedy the dangerous situation in the country".
He said his decision was in line with his convictions and his "obligation to the nation".
There have been calls for the whole cabinet to resign over Hariri's death.
After a long meeting in a Beirut hotel on Friday, the opposition said sit-ins should be held until the "illegitimate regime" resigned.
They also called for the suspension of political and legal debates in parliament until "the truth is uncovered" about Hariri's death.
Hariri had been prime minister for much of the last 15 years
The opposition says it wants a representative government to be formed which would then oversee the departure of Syrian troops from Lebanon.
The opposition had discussed whether its 40 deputies should resign en masse from the 128-member parliament. The BBC's Kim Ghattas in Beirut says they opted to stay on to ensure they have a hand in drawing a new electoral law ahead of legislative elections due in May.
The meeting was not attended by the leading opposition figure, Walid Jumblatt. He stayed away for "security reasons", aides said.
It was not clear what form of protest the opposition's hoped-for uprising would take.
Pro-government officials described the opposition's call as undemocratic.
The Damascus authorities have denied involvement in the bombing, which killed Hariri and 14 others.
Crowds of Lebanese of all religious faiths have been gathering at Hariri's grave since his funeral on Wednesday.
For many Lebanese, Hariri - a self-made billionaire businessman - symbolised the revival of their country after years of bloody civil war.