The Libyan capital's Mitiga airport was evacuated on Tuesday and civilian flights were repeatedly suspended as rival armed groups clashed nearby, officials said.
Flights had restarted around midday on Tuesday after being suspended for several hours during the morning and the previous evening, Mitiga spokesman Khaled Abukhrais said. But by late afternoon heavy gunfire resumed and the airport was shut.
"Unfortunately the air space has closed again and the airport has been evacuated for the safety and security of passengers and workers, due to renewed clashes," an airport statement said.
Mitiga is a military air base near the centre of Tripoli that has also hosted civilian flights since the international airport was largely destroyed by fighting in 2014.
The clashes began when the Special Deterrence Force (Rada), a group that controls Mitiga and operates as an anti-crime unit aligned with the UN-backed government, conducted raids in the nearby neighbourhood of Ghrarat.
Rada spokesman Ahmed Bin Salem said the group targeted in the raids had tried to attack the airport area after a wanted drug dealer had been killed when he fired on a Rada patrol.
"The area of Ghrarat is now under the control of our forces and it's being treated as military zone so we can clear any resistance," Bin Salem said.
One member of Rada had been killed and two wounded, and there were several casualties among their opponents, he said.
Tripoli is split among various armed groups that have built local power bases since Libya's 2011 revolution.
There have been fewer heavy confrontations in the capital since groups linked to a previous, self-declared government were pushed out of the city earlier this year, but armed skirmishes, kidnapping and other criminal activity are still common.