Forces allied with Libya's United Nations -supported government in Tripoli said on Thursday that they have wrestled another key town from their rivals who have been trying to capture the Libyan capital for over a year.
"In the event Turkish interests in Libya are targeted, this will have very grave consequences", Turkish Foreign Ministry spokesman Hami Aksoy said.
On Monday, the GNA of Fayez al-Sarraj seized al-Watiya airbase in Tripoli's southwestern desert reaches.
Turkish presidential spokesman Ibrahim Kalin was also quoted as saying by broadcaster NTV that attacks on Turkish positions would prompt heavy retaliation.
Fighters for the Government of National Accord (GNA) said they had advanced into several districts and overrun a military camp.
Turkey's state-run Anadolu Agency said the GNA carried out five air operations against forces loyal to Haftar in the past 24 hours.
Turkish drones and air defences appear to have played a key role in GNA advances in recent weeks, with repeated claims of attacks on LNA supply chains from the east.
Haftar's LNA, backed by the United Arab Emirates, Egypt, and Russian Federation, has been unable to make significant progress since early on in its campaign.
Last year, Middle East Eye reported that as Haftar's offensive against Tripoli began, the LNA had about 15 operational aircraft: eight MiG-21s (one was shot down over Tripoli by a Chinese-made air defence system), three MiG-23s, two Su-22s and two Mirage F1s.
On Wednesday, Haftar's forces announced they would withdraw up to 3 kilometers from the front line around Tripoli in a humanitarian gesture aimed at giving the residents a respite from the fighting to celebrate Eid al-Fitr.
The LNA still holds all of eastern Libya and much of the south, including most oil facilities.
Turkey has had frayed ties with the UAE and Egypt for years.