Forces loyal to Gen Haftar are suspected to have launched an attack at Mitiga airport
The forces of the Libyan military strongman Gen Khalifa Haftar say they will target any civilian or military plane using the airport that serves the capital, Tripoli.
A spokesman said this was a final warning.
Earlier rocket fire had forced Mitiga airport to close.
Gen Haftar's forces accuse Turkey of using it as a base from which to target them.
The Turks give military support to Libya's UN-backed government, which holds Tripoli.
For many months Gen Haftar has been waging a major offensive aimed at capturing the city.