(CNN) Tripoli's only working airport was targeted in an airstrike on Monday, as forces loyal to renegade Libyan general Khalifa Haftar continued their advance on the capital, ignoring international calls for a truce.

Mitiga airport, in the eastern quarter of Tripoli, was shuttered after it was attacked by Haftar's so-called Libyan National Army (LNA). Libya's United Nations-backed government, the Government of National Accord (GNA), quickly condemned the aerial bombardment, calling it a war crime.

There is also fighting around Tripoli's international airport, 15 miles south of the city center, which has not been operational for years. The GNA admitted Monday that it temporarily lost control of the site to Haftar's fighters.

"Haftar forces attacked Tripoli four days ago, mainly from the south and got as far as controlling Tripoli international airport," a GNA official told CNN Monday. "As of yesterday and today, Monday, Haftar forces have been pushed back and Tripoli secured."

The same official said militias from the coastal towns of Misrata and Zawia -- which are not under the GNA's direct control -- deployed troops to the capital as part of the counter-offensive against the LNA.

Luggage trolleys lie in front of the gate of the Mitiga airport after it was attacked Monday.

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