Residents tweeted they heard heavy weapons and artillery.
Local media showed footage of gunbattles in Tripoli's residential areas.
Several cars were set ablaze.
The clashes erupted after the parliament-appointed Prime Minister Fathi Bashagha tried to take control of government from a rival administration that has refused to cede power.
Bashagha was attempting to enter the city and set up his offices.
Baschagha attempted to enter Tripoli but quickly left after resistance from local militias.
His office said he wanted to prevent bloodshed and protect citizens.
In a controversial move in February, the parliament in eastern Libya elected former interior minister Baschagha as the new head of government, even though Abdul-Hamid Dbeibeh holds this office.
Dbeibeh has refused to step down, insisting he will hand over power only to an elected government.
Dbeibeh's interim government took office in March 2021 after it was elected in a United Nations-brokered process with the aim of leading Libya until polls planned for December that never took place.
The election is part of a United Nations-backed plan to end a decade of chaos in Libya that started when long-time ruler Muammar Gaddafi was toppled in 2011.
Libya has become a battleground, drawing in foreign powers.
A country-wide ceasefire came into effect in October 2020.
Since then, there have been occasional fights.
"Bashagha seems to have vastly underestimated the likelihood of Tripoli-based groups mobilising against him," Libya expert Emadeddin Badi said.
12°C