Ancient ruins in Palmyra
Ancient ruins in PalmyraReuters

UNESCO chief Irina Bokova on Thursday welcomed a push to recapture the Syrian heritage city of Palmyra from Islamic State (ISIS) jihadists, who have destroyed many of the ancient site's monuments.

"For one year, Palmyra has been a symbol of the cultural cleansing plaguing the Middle East," the head of the UN's cultural body said, according to the AFP news agency, adding that she welcomed the effort to retake "the Palmyra archaeological site, martyr city inscribed on the UNESCO world heritage list".

The statement came after Syrian troops backed by Russian warplanes and allied militia entered Palmyra on Thursday, after launching a desert offensive early this month, according to the Syrian Observatory for Human Rights.

ISIS overran Palmyra, known as the "Pearl of the Desert", last May and it has since blown up UNESCO-listed temples and looted relics that dated back thousands of years.

"The destruction of temples of Baal Shamin and Bel, the funeral towers and the Triumphal Arch are an immense loss for the Syrian people and the world," Bokova said in the statement quoted by AFP.

ISIS has used Palmyra's grand amphitheatre for a massacre in which child members of the group killed 25 Syrian soldiers, execution-style, in front of residents.

It also beheaded Palmyra's 82-year-old former antiquities director in August.

A Syrian military source said the army had entered Palmyra from the northwest after seizing control of part of the historic Valley of the Tombs.

"As soon as security conditions allow, UNESCO is ready to go to Palmyra with those responsible for Syrian antiquities on a mission to evaluate damage and protect the priceless heritage of the city," Bokova added.

"The deliberate destruction of heritage is a war crime, and UNESCO will do everything in its power to document the damage so that these crimes do not go unpunished."

Syria's antiquities chief Maamoun Abdelkarim earlier hailed the "imminent" recapture of Palmyra, vowing to rebuild monuments the jihadists had destroyed.

AFP contributed to this report.