The forces pushed into Qaryatain under the cover of Russian air strikes and dealt another setback to IS extremists in Syria.
The town has a Christian majority and had been under Islamic State (IS) control since August last year.
anti-tank missiles captured during the militants attack
It is thought dozens of Qaryatain's Christians and other residents have been abducted by the extremists.
The town lies midway between Palmyra and the capital, Damascus.
An activist group that monitors the Syrian civil war said that government forces are now in control of most of the town after IS fighters withdrew to its eastern outskirts.
This advance came a week after Syrian forces recaptured Palmyra from IS and it is strategically significant for the government side and means that IS no longer has a main base in central Syria.
Christians made up about 10% of Syria's pre-war population of 23 million people.
tank fires at Syrian troops and pro-government gunmen
The Syrian army command said in a statement that troops have "restored security and stability to Qaryatain and farms surrounding it", and the British-based Syrian Observatory for Human Rights said intense fighting took place to capture all parts of the town.
The observatory's chief Rami Abdurrahman said that IS fighters are still in control of small areas east of the town but "are on the verge of collapse".
IS has suffered major defeats in Syria in recent months amid intense air strikes by Russian warplanes.
