Forces loyal to the Assad regime have entered Palmyra as part of an operation to oust Daesh militants from the ancient city, a monitoring group says.

"The Assad regime troops accompanied by their allies, backed by Russians planes have entered the first neighborhood of al Mutakadeen which is located in the western sector of city," Rami Abdel Rahman, head of the Britain-based Syrian Obsevratory for Human Right reported.

Abdel Rahman said the regime is now fully controlling the western and north-western sectors of the outskirts of the city of Palmyra. He added that reports are saying that Daesh militants have withdrawn from inside the city of Palmyra.

Daesh has put up a strong fight, managing to foil various attacks by the Assad regime in recent days. Palmyra, which is a UNESCO world heritage site, was seized by Daesh terrorists in 2015, before being recaptured by Assad regime in March 2016. However, Daesh retook Palmyra in an unexpected offensive in December 2016 while the Assad regime and its allies were focused on gaining ground in Aleppo against moderate Syrian opposition forces. Daesh has ravaged the city's celebrated heritage, blowing up funerary towers and carrying out mass executions in the city's Roman theatre. Last month, Daesh destroyed Palmyra's tetrapylon monument, while satellite images showed damage to the theatre's facade. The new destruction was condemned by the United Nations as a "war crime." On Wednesday, two funeral busts damaged by Daesh after it first captured Palmyra were brought back to Syria after being restored in Italy.