Syrian pro-government forces advanced to the edge of the famed ancient city of Palmyra on Wednesday, eyeing a major symbolic victory over the Islamic State jihadist group, a monitor said.

"The regime forces are now two kilometres (a little more than a mile) away on the south side and five kilometres (three miles) away on the west side," Syrian Observatory for Human Rights director Rami Abdel Rahman told AFP.

IS seized the city dubbed the "Pearl of the Desert" in May last year, sending shock waves around the world as they demolished some of the most treasured monuments of its UNESCO-listed World Heritage Site.