Islamic State group fighters have advanced to the gates of ancient Palmyra on Thursday, raising fears the Syrian world heritage site could face destruction of the kind the jihadis have already wreaked in Iraq.

Isis fighters were battling Syrian troops less than two kilometres (barely a mile) from the remains of one of the most important cultural centres of the ancient world, Syria’s director of antiquities said.

The jihadists reached the oasis town after a lightning advance across the desert in which they overran government forces in fierce fighting that cost the lives of 110 combatants, the Syrian Observatory for Human Rights said.

“Palmyra is under threat,” said the Observatory director, Rami Abdel Rahman.

Antiquities director Mamoun Abdulkarim said he was in touch with colleagues still in Palmyra every half hour

“Isis has not entered the city yet, and we hope these barbarians will never enter,” Abdulkarim told AFP.

Unesco describes Palmyra as a heritage site of “outstanding universal value”.

The ancient city stood on a caravan route at the crossroads of several civilisations and its first- and second-century temples and colonnaded streets mark a unique blend of Graeco-Roman and Persian influences.

The jihadi advance on the well-preserved remains came as an international conference was under way in Cairo to address the destruction already wreaked by Isis on the ancient sites of Nimrud and Hatra in Iraq.

Foreign affairs and antiquities officials from 11 Arab countries gathered in Egypt to condemn the jihadis’ demolition of Iraq’s heritage, with sledgehammers, bulldozers and high explosives.

Abdulkarim said Syria had not been invited to the conference and that he had not been contacted by any of those attending about the threat to Palmyra.

He told AFP that antiquities officials would try to ensure the safety of artefacts found in archaeological digs over the years, which are housed in an adjacent museum.

“We can protect the statues and artefacts, but we cannot protect the architecture, the temples,” he said.

“Isis will just destroy it from the outside.”

Abdulkarim said he had no doubt that if Palmyra fell to the jihadis, it would suffer a similar fate to ancient Nimrud, which they blew up earlier this year.

“If Isis enters Palmyra, it will spell its destruction.

“If the ancient city falls, it will be an international catastrophe. It will be a repetition of the barbarism and savagery which we saw in Nimrud, Hatra and Mosul.”

It would not be the first time that government troops have lost control of Palmyra. Rebels held the site from February to September 2013 before government troops recaptured it.

One of the ancient city’s masterpieces, the Temple of Baal, suffered some damage during the accompanying artillery exchanges.

But those rebels did not share the fanatical devotion of Isis to demolishing all of the region’s pre-Islamic heritage.

There was ferocious fighting as the jihadists overran the town of Al-Suknah on Wednesday in their drive across the desert towards Palmyra.

Provincial governor Talal Barazi said that 1,800 families who had fled the advancing jihadis were being sheltered in reception centres in the adjacent modern town of Tadmur.

Both sides suffered heavy losses in the battle for Al-Suknah, including senior commanders, the Observatory said.

The army lost 70 men, including six officers. Isis lost 40 men, including two commanders, one of them the leader of the offensive.

Jihadi websites named him as Abu Malik Anas al-Nashwan, who appeared in an Isis video showing the beheadings of 28 Ethiopian and Eritrean Christians in Libya last month.