The Syrian army and its allies seized control of at least 30 km (19 miles) of Syria's border with Jordan from rebels in an attack on Thursday, two rebel groups and a Syrian military source said.
A military media unit run by Hezbollah, a close ally of the Syrian government, said the army and its allies had gained control over all checkpoints and border posts on the border in Sweida, one of four Syrian provinces that border Jordan.
Rebel groups, some of them backed by Western and Arab states, still control much of Syria's southwestern frontier with Jordan and Israel.
Sweida province was not included in a U.S.-Russian brokered ceasefire that took effect in nearby areas of the southwest in July.
Said Saef, spokesman for the Western-backed rebel group Martyr Ahmed Abdo brigade, said Thursday's attack came from two sides in Sweida's east countryside. "Most of the eastern Sweida countryside is now in the hands of the regime," he added.
The army had advanced to the border and retaken posts it abandoned in the early years of the conflict when rebels took over large parts of south western Syria.
"They are now on the Jordanian border and back to outposts they had evacuated early in the conflict," said Saef.
Another rebel spokesman said the army gains were helped by a sudden pull-back by Jaish al-Ashair rebel group, which is backed by Jordan and had been responsible for patrolling that stretch of the border.
The Syrian military source said the army and its allies had taken more than 30 km of the border, and described the advance as a "big success".