Barricades were erected overnight to block or control access to protest sites in the capital where counterdemonstrators have previously tried to attack protesters, AFP journalists said.
An officer who spoke to AFP on condition of anonymity said the concrete barriers were intended to help security forces better control the sites and prevent further clashes.
After violence between protesters and security forces in Beirut on Saturday and Sunday night, and between counterdemonstrators and police on Monday night, the capital remained calm on Tuesday.
But tensions were recorded elsewhere in the country, as Lebanon awaits scheduled parliamentary meetings to name a new premier on Thursday, a required step to form a cabinet.
The unprecedented protests started on October 17 against a political elite deemed inept and corrupt. Protesters demand a complete overhaul of the ruling class and a new government formed of independent experts.
Prime minister Saad Hariri resigned on October 29, but bitter divisions between political parties have twice seen parliamentary consultations to name a new premier postponed.
On Tuesday night, young supporters of the Shiite Amal movement threw stones at anti-government protesters in the southern Shiite stronghold of Nabatieh, a witness said.
Unknown perpetrators set fire to a Christmas tree in the northern city of Tripoli, an AFP correspondent said.
On Monday night, dozens of supporters of the country's two main Shiite political parties set fire to cars and clashed with security forces trying to prevent them from reaching Beirut's main protest square.
Pressure to form a new government is compounded by the near collapse of the economy, already weakened by years of political deadlock and the impact of the eight-year-old war in neighbouring Syria.
The World Bank estimates that Lebanon is in recession, and has warned that the number living in poverty could increase from a third to half the population.