A spat has developed over military facilities inside the World Heritage Site of Palmyra, which according to a top Syrian archaeologist were built by Russia without permission. Satellite images appear to show a helicopter pad, two roads and accommodation blocks located inside the northern necropolis area of the site.

The American Schools of Oriental Research said the structures were "close to numerous above-ground and subsurface tombs and funerary temples", The Times reported. Head of the Syrian antiquities department Maamoun Abdulkarim told AP that he would have opposed the building of the base had he been consulted on it.

"We refuse to give permission even if it was for a small room to be built inside the site — whether it is for the Syrian army, Russian army or anyone else. We will never give such permission because this will be in violation of the archaeology law."

But Russia insisted that the Syrian authorities had given permission for what was a "temporary camp" that would give medical assistance to the local population, pointing out that Russian engineers had defused 18,000 explosives around Palmyra.

In a statement, Russian defence ministry spokesman Major-General Igor Konashenkov said: "The deployment of this temporary camp through the end of the demining effort has been fully agreed upon with the ministry of culture and other Syrian agencies."

The protection of the ancient site from Isis militants came as reports emerged that an earthquake around it was triggered after Isis blew up the Shaer gas field, in the central province of Homs.

The Syrian Observatory for Human Rights said that Isis carried out three huge explosions, blowing up Shaer's pumping stations. A 4.4 magnitude earthquake was recorded in the area, shaking Palmyra, which is located about 30 miles (48km) south east.

Syria's army recaptured Palmyra from Isis in March. Soon after, a Russian orchestra performed a concert in the historic place, sparking criticism in some quarters over whether it was appropriate.