Libya's UN-recognized Government of National Accord (GNA) on Sunday warned east Libyan forces against imposing a "no-fly zone" over western Libya, as reproted by Anadolu Agency.
On Saturday, a spokesman for forces led by military commander Khalifa Haftar announced a no-fly zone over western Libya.
In a statement, the GNA-affiliated Interior Ministry said any action threatening civil aviation and airports "amounts to crimes punishable under national and international law".
In April, Haftar's forces launched a military campaign to capture Tripoli from the internationally-recognized GNA, but have so far failed to make advance beyond the city's outskirts.
Since the ouster of late ruler Muammar Gaddafi in 2011, two seats of power have emerged in Libya, one being in eastern Libya supported mainly by Egypt and the United Arab Emirates, and another in Tripoli, which enjoys UN and international recognition.