MPs fled the building after heavily armed attackers tried to storm it. Some eyewitnesses say the gunmen were from the powerful Zintan Brigade of former rebel fighters.
However a paramilitary force supporting a retired general, Khalifa Haftar, claimed it was behind the assault.
Authorities are struggling to contain militias that control parts of Libya.
A planned new constitution remains unwritten and the country has had three prime ministers since March.
On Sunday, the gunmen launched their assault on parliament in armoured vehicles. Black smoke rose above the building as militiamen loyal to the government responded.
The building was largely empty, with reports that officials had been warned in advance and had left the area.
The BBC‘s Rana Jawad in Tripoli says the sporadic rumble of heavy arms being fired is still being heard across the city.
Gen Haftar’s militia on Friday launched a major air-and-ground attack against Islamist militants in the eastern of Benghazi.
The government condemned the attack and declared a no-fly-zone in the city, threatening to shoot down any military aircraft.
At least 70 people died in the fighting.