Men attempt to pull down barbed wire fencing after parts of the capital were cordoned off.
Police in Beirut have fired warning shots and thrown tear gas at hundreds of angry protesters attempting to storm the Prime Minister's office in Beirut.
Clashes erupted during the funeral for top intelligence chief Brigadier General Wissam al Hassan, who was killed in a massive car bombing on Friday.
Forces had earlier set up road blocks and cordoned off Beirut's Martyrs' Square as well as boosting security in the capital.
Currently, the scene has quietened to a tense stand-off, which some protesters refusing to leave the area.
Mr al Hassan, 47, was a powerful opponent of Syria in Lebanon and headed an investigation over the summer that led to the arrest of former information minister Michel Samaha, a politican who was one of Syria's most loyal allies.
He was among eight people killed in the attack on Friday, which many have blamed on the Syrian regime.
The protesters believe the government is too close to Syria and its ally in Lebanon, the Shiite group Hizbollah.
They are calling for Prime Minister Najib Mikati to quit over Mr al Hassan's assassination.
Even before the bombing, the civil war in neighboring Syria had set off violence in Lebanon and deepened tensions between supporters and opponents of President Bashar Assad's regime.
The attack heightened fears that Lebanon could easily plunge back into cycles of sectarian violence and reprisal that have haunted it for decades.
Dozens of anti-Syrian protesters erected eight tents near the cabinet headquarters in central Beirut, saying they will stay until Prime Minister Najib Mikati's government, which is dominated by the Shiite militant group Hizbollah and its allies, resigns.
Hizbollah is Syria's most powerful ally in Lebanon, which for much of the past 30 years has lived under Syrian military and political domination.
Syria's hold on Lebanon began to slip in 2005, when former Prime Minister Rafik Hariri, an opponent of Syria, was assassinated by a truck bomb along Beirut's Mediterranean waterfront.
Syria denied any role, but broad public outrage in Lebanon expressed in massive street protests forced Damascus to withdraw its tens of thousands of troops from the country.
For years after the pullouts, there was a string of attacks on anti-Syrian figures in Lebanon without any trials for those responsible.
Al Hassan will be buried in Martyrs' Square next to the late Hariri.