Russian-backed Syrian government forces and their allies fought their way into Palmyra on Wednesday, driving back Islamic State militants who have held the historic city since December, the Syrian Observatory for Human Rights monitoring group reported.
A Hezbollah-run media outlet earlier reported that the Syrian army and its allies had recaptured the Palmyra citadel, on the city's western outskirts, and seized a modern palatial complex to the southwest.
Islamic State has captured Palmyra, whose ancient ruins are a UNESCO World Heritage Site, twice during Syria's six-year conflict.
The army recaptured the city from the ultra-hardline group in March last year, but Islamic State seized it again in December.
The group has razed ancient monuments during both of its spells in control of Palmyra - destruction the United Nations has condemned as a war crime.
A Syrian military source told Reuters earlier on Wednesday: "The army's entry to the city will begin very soon."