The Syrian army and its allies have advanced to within 10 km (7 miles) of al-Mayadin, bringing them close to a city seen as the current main base of Islamic State.
They have won control of positions and heights parallel to the main road linking Deir al-Zor and al-Mayadin, located on the Euphrates in eastern Syria, the media unit said.
A war monitor, the Syrian Observatory for Human Rights, said on Thursday the army was only 6 km from al-Mayadin.
Islamic State has staged fierce counter attacks in central Syria in recent days, testing the army's control of an area seized in a months-long eastward offensive.
Backed by Russian air power, the army has continued its advance towards al-Mayadin from Deir al-Zor along the Euphrates valley.