An unidentified warplane bombarded Islamist militia positions near Tripoli airport overnight, leaving at least 10 people dead, a spokesman for an alliance of Libyan militias said on Saturday.
The aircraft targeted an army base to the south of Tripoli and a nearby warehouse, Mohammed al-Ghariani, spokesman for Fajr Libya (Libyan Dawn), said on An-Nabaa television station.
Islamist fighters including a group from Misrata, east of Tripoli, have seized the army base from a rival militia from Zintan, west of the capital.
During a lull in the fighting, the Islamist militia organised a visit on Thursday for Libyan journalists to prove they had captured the building, which was the army's headquarters during the regime of long-time dictator Moamer Kadhafi, overthrown in 2011.
Ghariani said "at least 10 men" from Fajr Libya died and 20 others were wounded in Friday night's raid, which followed an initial air strike last Monday.
An-Nabaa television, which is close to the Islamists, later raised the toll to 13 deaths and 30 wounded, but without giving a source.
"We haven't identified the plane that carried out the raid, just like those that attacked us on Monday," the Fajr Libya spokesman said.
Rogue general Khalifa Haftar, who opposes the Islamists and favours the Zintan militia, claimed Monday's raid but specialists doubted his ability to carry out such at attack.
An air force unit which has refused to join an offensive launched by Haftar in the eastern city of Benghazi said the aircraft were "foreign, not Libyan".
It said Libyan aircraft are not equipped to make night flights and cannot be refuelled in flight, particularly if they take off from remote air bases controlled by Haftar's forces.