A new air strike hit the Libyan capital's sole operational airport on Tuesday, a day after a raid claimed by forces loyal to a prominent anti-Islamist general, witnesses said.

Mitiga air base, in an eastern suburb of Tripoli, has been the city's only working airfield since damage from heavy fighting forced the closure of its civilian airport in July.

"We heard the roar of a plane then several explosions around the airport perimeter," a witness told AFP.

He had no word on any casualties or damage.

On Monday, a low-flying fighter jet fired two missiles at the air base, which, like the rest of the capital, is controlled by Islamist-backed militia opposed to the internationally recognised government.

A security source said the strike caused no damage to the terminal or runway, although flights were temporarily diverted to Misrata airport, 200 kilometres (125 miles) east of Tripoli.

UN envoy Bernandino Leon called Libya's internationally recognised Prime Minister Abdullah al-Thani to demand an end to strikes on Mitiga airport and appeal for talks with his rivals, Thani's office said.

The office reported a "pre-emptive strike" that targeted groups from Fajr Libya, an anti-government Islamist coalition that it said was armed with warplanes capable of destroying state infrastructure.

Thani said in the statement that he was ready for dialogue but only once his rivals recognised the legitimacy of the parliament and withdrew from Tripoli, allowing his cabinet to return.

Forces loyal to retired general Khalifa Haftar, who has been leading a separate government-backed offensive against Islamist militia in Libya's second city Bengahzi, said they carried out Monday's air strike.

More than three years after dictator Moamer Kadhafi was toppled and killed in a NATO-backed revolt, Libya is awash with weapons and powerful militias, and run by rival governments and parliaments.

Thani's government has been based in the remote east of the country since the militia takeover of the capital in August.

All three main cities -- Tripoli, Benghazi and Misrata -- are largely controlled by militias opposed to Thani's government.