Syrian regime troops and allied forces captured the city of Mayadeen from the Islamic State group on Saturday, state media said.
"Units of our armed forces, in cooperation with allied forces, have regained control of the city of Mayadeen in Deir az-Zour, killing a large number of terrorists and destroying their weapons," state media said, citing a military source.
"Our units are chasing down remaining members of Daesh fleeing the city amid a collapse in their ranks, and the engineering units are removing mines and explosives planted by the terrorists in the streets and square of the city," the source added.
The capture comes despite IS fighters managing last week to push advancing troops out of the eastern city, just two days after they entered it.
A renewed push by the Russian-backed Syrian troops saw them re-enter the city, and sever the main road leading from it to the IS stronghold of Albu Kamal on the Iraqi border to the east.
The advance left IS fighters in the city with the Euphrates River as their only route to escape.
Mayadeen's loss is the latest in a string of blows for IS, which is on the verge of losing its former de facto Syrian capital Raqqa to the US-backed fighters of the Syrian Democratic Forces (SDF).
The Islamic State's control of the Deir az-Zour province is also crumbling in the face of parallel regime and SDF offensives.
Last month, Syrian regime forces broke an IS siege of nearly three years on regime-held parts of the provincial capital.
Syrian forces have now encircled remaining IS positions in the city after capturing new areas east the Euphrates River, state news agency SANA reported on Saturday.
IS have been all but defeated in neighbouring Iraq, where the last pockets of territory are being mopped up by the Iraqi army.