Fears are mounting that Islamic State terrorists could destroy an ancient Roman site in Libya which they have seized in their march towards the capital Tripoli.

ISIS fanatics travelling in 30 pick-up trucks stormed the coastal city of Sabratha on Wednesday night after three of their men were captured by a rival militia.

Black-clad militants overpowered residents and set up checkpoints in the city, which is just 50 miles from Tripoli, before successfully retrieving the three men.

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Ancient Roman site: There are concerns that the priceless landmarks in the Libyan city of Sabratha (file picture), a Unesco world heritage site, will be destroyed by Islamic State

Temple of Baalshamin: In Syria, ISIS has already blown up historic sites at the Unesco world heritage site in Palmyra, including temples, columns and sculptures which the Islamist group claims depict ‘false idols’

There are now concerns that the priceless landmarks in the city, a Unesco world heritage site, will be destroyed by ISIS, including a 3rd-century Roman amphitheatre.

In Syria, the group has already blown up historic sites at the Unesco world heritage site in Palmyra, including temples, columns and sculptures which the Islamist group claims depict ‘false idols’.

Yesterday, Libya's rival parties met in Tunis for talks on a disputed United Nations-brokered deal backed by the international community to set up a unity government in the conflict-ravaged country.

The talks were to focus on moving the process forward ahead of an international meeting on Libya scheduled for Sunday in Rome, the United Nations Support Mission in Libya said.

Priceless: A spectacular third-century Roman amphitheatre in the Unesco world heritage city, which there are now concerns will be destroyed by ISIS

Threat: In Syria, the group has already blown up historic sites at the Unesco world heritage site in Palmyra, including temples, columns and sculptures. Pictured, Sabratha

Key discussion: Yesterday, Libya's rival parties met in Tunis for talks on a disputed United Nations-brokered deal backed by the international community to set up a unity government in the conflict-ravaged country

Gaining ground: An ISIS militant holds the terror group's flag in August as he stands on a tank they captured from Syrian government forces, in the town of Qaryatain, south-west of Palmyra, in central Syria

The UN envoy for Libya, Martin Kobler, and representatives of rival parliaments took part in the discussions at a hotel in a Tunis suburb, with foreign diplomats invited as observers.

Mr Kobler, who only took over from his predecessor last month, said he felt ‘very encouraged’ by what he heard in the talks, adding that the parties would meet again on Friday.

US Secretary of State John Kerry will co-chair Sunday's talks in Rome with his Italian counterpart Paolo Gentiloni. Representatives from Russia, Britain, China and France will also be attending.

The discussions come at a time of growing international concern that the ISIS jihadist group has been exploiting the chaos in Libya to take root in the country.