Beirut, May 21 (IANS/EFE): Islamic State forces on Wednesday seized control of the ancient city of Palmyra, Syria's head of antiquities said.

"This is a disaster for the entire world, not just for the Syrians," Maamoun Abdul Karim said by telephone from Damascus, referring to the threat posed by IS to Palmyra's famed 2,000-year-old ruins.

Authorities managed to remove around 100 statues before IS fighters reached the Roman-era archaeological site on the city's southwestern edge, Abdul Karim said.

Small groups of government soldiers and other opponents of IS remain in and around Palmyra, he said.

Syrian state television reported that army troops and pro-government militias withdrew after evacuating the remaining civilian residents from Palmyra, significant not only for its archaeological treasures but also for its strategic location in the central province of Homs.

Army units remain on roads leading to Palmyra and the air force is carrying out strikes against "concentrations of terrorists who have infiltrated" the city, according to state television.

Samer al-Homsi, an opposition activist, said via internet that IS established full control over Palmyra after the "sudden" withdrawal of government forces in the direction of the phosphate mines at Khnifiss.

IS fighters entered Palmyra from the north early on Wednesday, three days after being driven out by the army and its allies.

A week into their latest offensive in Homs province, the jihadis have taken several cities, as well as the al-Arak and al-Hil gas fields.

Palmyra, an oasis in the Syrian desert, was a leading cultural centre in the 1st and 2nd centuries A.D. and later became an important stop for Silk Road caravans.

Prior to the start of Syria's civil war, in March 2011, the Palmyra ruins were one of the country's foremost tourist attractions.

The head of the UN Educational, Scientific and Cultural Organisation, which has designated the Palmyra ruins as a World Heritage Site, appealed on Wednesday for a cease-fire.

"I am deeply concerned by the situation at the site of Palmyra. The fighting is putting at risk one of the most significant sites in the Middle East, and its civilian population," UNESCO Director General Irina Bokova said in a statement.