In Iraq, armed forces are said to be bearing down on the IS-held city of Mosul
Syrian government forces have entered the Islamic State-held city of Palmyra, according to state television.
IS has occupied the city since May last year, demolishing several of its ancient structures and carrying out a series of beheadings in the iconic amphitheatre.
The fighting is reportedly concentrated near the archaeological site on the southwestern edge of the town.
One Syrian soldier told the national TV station that IS would be "crushed under the feet of the Syrian Arab Army".
One Syrian official said that forces are less than a mile from the heart of the city, and roads are being cleared of mines and explosives.
In advance of the latest assault, IS used loudspeakers to tell the 15,000 civilians still living in Palmyra to leave the city.
Palmyra, which linked the Roman Empire to Persia and the East, is said to have been one of the most important cultural centres of the ancient world.
UNESCO has called the destruction of Palmyra's monuments war crimes and says IS seeks to wipe out evidence of Syria's diverse heritage.
Meanwhile in Iraq, armed forces are bearing down on the IS-held city of Mosul.
The first stage of an operation aimed at liberating Mosul started with an offensive against IS in the northerly Nineveh province.
It was launched from the Makhmour area where Iraqi troops have been deployed in recent weeks.
Troops are being backed by air power from a US-led coalition and Kurdish peshmerga forces.
Several villages have already been recaputured.
Mosul was home to two million people before being taken over by IS, and it is the largest city controlled by the group.
It is still heavily populated which makes it more complicated to retake.
A military statement urged civilians to stay away from buildings used by the insurgents, warning that they would be targeted in days to come.