Syrian state television says government forces have now fought their way into the ancient city of Palmyra.
The army has been trying to retake Palmyra since it was seized by ISIL fighters in May 2015.
Clashes have raged in the historic city in recent days after government forces took control of a nearby hill.
Activists say Syrian and Russian planes provided air cover.
Palmyra is a key point on the mostly-ISIL held eastern Syrian province of Deir el Zor.
It was seized by ISIL in May 2015 and has remained in the group’s hands since then.
Shuttle diplomacy continues between the main powers charged with bringing the Syrian conflict to an end.
US Secretary of State John Kerry has discussed the fragile truce in Syria with his Russian counterpart Sergei Lavrov in Moscow.
Kerry is due to meet Vladimir Putin later in the trip.