Syrian government forces and their allies pushed forward against Islamic State fighters to reach the outskirts of the historic city of Palmyra on Wednesday, state media and a monitoring group said.

Clashes raged around Palmyra after government forces took control of most of a nearby hill with air cover from Syrian and Russian warplanes, the Britain-based Syrian Observatory for Human Rights said.

State news agency SANA quoted a military source who said the army and allied militia advanced in the hills outside Palmyra and towards a road junction "after eliminating the last terrorist Daesh groups there", referring to IS fighters.

The Syrian army is trying to recapture Palmyra, which IS seized in May, to open a road to the mostly IS-held eastern province of Deir al-Zor.

Russian President Vladimir Putin, who said last week he was withdrawing most Russian forces after a five-month military intervention which turned the tide of Syria's war in favour of President Bashar al-Assad, has predicted the Syrian army will retake Palmyra soon.