The fighting between the 444 Brigade and the Al-Radaa Force, or Special Deterrence Force, erupted on Monday night and carried over into Tuesday, an interior ministry official said.
"Clashes affected several areas of Tripoli's eastern suburbs, in Ain Zara south of Tripoli, pitting the forces of 444 Brigade against those of Al-Radaa," the official told AFP on condition of anonymity.
"Tensions arose" soon after it was announced "the Al-Radaa Force had arrested the head of the 444 Brigade, without explaining whether this was on judicial orders or for other reasons," the official said.
There were no immediate reports of any casualties from the fighting which was still underway on Tuesday morning, and which the official said had forced "the closure of roads around Mitiga airport."
Air traffic was stopped at Mitiga airport and flights were diverted to Misrata, about 180 kilometers (110 miles) to the east, and aircraft that had been parked on the tarmac were moved away.
The Health Ministry appealed to citizens to donate blood to help casualties. Usama Ali, a spokesperson for the ambulance service, said 19 people had been injured and 26 families evacuated from a strife-hit district.
Dark smoke hung over parts of the city early on Tuesday and the sound of heavy weapons rattled through the streets, a Reuters journalist in Tripoli said. Residents and local media reported fighting in different parts of the capital.
The clashes between the 444 Brigade and the Special Deterrence Force, which both backed the interim Government of National Unity, GNU, during brief battles last year, shatter months of relative calm in Tripoli.
Libya has had little peace or security since a 2011 NATO-backed uprising overthrew dictator Muammar Gaddafi and it split in 2014 between warring eastern and western factions.
An assault by eastern forces on Tripoli, in the west, collapsed in 2020 leading to a ceasefire that has halted most major warfare. Turkey, which backed the Tripoli government, maintained a military presence in Libya.
However, there has been little progress towards a lasting political solution to the conflict and on the ground armed factions that have gained official status and financing continue to wield power.
Last year, factions backing a rival government declared by the eastern-based parliament launched a doomed attempt to oust Abdul-Hamid Dbeibah, who heads the Tripoli-based government, leading to a day of heavy clashes in Tripoli. Sporadic fighting has also this year rocked the city of Zawiya, west of the capital.
A resident of the Tarik Shok area of southern Tripoli said he could hear fighting when he went to bed at 1:30 am and more strongly when he woke up at 7:30 am.
"We can hear heavy gunfire since early morning. My family lives in the Khalat Furjan area about 7km (4 miles) away and they also hear clashes," he said.
Footage circulating on social media, which Reuters was unable immediately to authenticate, showed Tripoli residents blocking roads with burning tires.
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