Syrian government forces seized a final stretch of highway linking the eastern city of Deir el-Zour to the capital Damascus on Sunday in further advances against Islamic State, a Hezbollah-run media unit reported.
Troops moving in from the west linked up with forces already in Deir el-Zour at the Panorama entrance to the city, bringing the whole road under their control for the first time in years, it said.
The Syrian army and its Iran-backed allies, which include Lebanese Hezbollah, this week broke a three-year siege by the jihadists of a government-held enclave of Deir el-Zour and an adjacent air base.
The rapid government advances, accompanied by Russian air strikes, are squeezing Islamic State in its last major Syria stronghold, as U.S.-backed forces separately oust the jihadists from areas they hold to the east, on the other side of the Euphrates river.
The U.S.-backed Syrian Democratic Forces (SDF) said they had made further gains against IS a day after announcing an operation to capture northern and eastern parts of Deir el-Zour province.
Syrian state TV broadcast footage of Syrian officers who had been holed up in Deir el-Zour emotionally greeting their superiors after being surrounded by IS since 2014.
The United Nations has estimated that some 93,000 people were living in "extremely difficult" conditions in government-held parts of Deir el-Zour, supplied by air drops to the air base.
Islamic State has lost nearly half of its territory across both Iraq and Syria, but still has 6,000-8,000 fighters left in Syria, the United States-led coalition has said.