Turkey warned on Thursday that attacks on its interests in Libya by Khalifa Haftar's forces will have "very grave consequences", after advances by the country's Turkish-backed government.
Ankara has provided military support to the Government of National Accord (GNA) in Libya, which has been battling to fend off a year-long offensive by Haftar's forces to take control of the capital Tripoli.
Turkish Foreign Ministry spokesman Hami Aksoy said Haftar's Libyan National Army (LNA) had received warplanes with "foreign support" and that they had vowed to target Turkish positions in Libya with an air campaign.
"In the event Turkish interests in Libya are targeted, this will have very grave consequences," Aksoy said. Presidential spokesman Ibrahim Kalin was quoted as saying by broadcaster NTV that attacks on Turkish positions would prompt heavy retaliation.
In what could be their most significant advance for nearly a year, the GNA took control of the Watiya air base south-west of Tripoli on Monday.
Haftar's LNA, backed by the United Arab Emirates, Egypt, and Russia, has been unable to make significant progress since early on in its campaign. But it still controls eastern and southern Libya, including most of the country's oil facilities, and the city of Sirte, at the centre of Libya's Mediterranean coastline.
Turkey has had frayed ties with the UAE and Egypt for years. It has accused Abu Dhabi of bringing chaos to the region through its interventions in Libya and Yemen, and has called on Russia to halt its support for Haftar.