Russian jets pounded rebel-held areas of the Syrian city of Deraa on Tuesday for a second day in the first such intensive bombing campaign since Moscow's major intervention in Syria more than a year ago, rebels and witnesses said.

Rebel groups on Sunday stormed the heavily garrisoned Manshiya district in a battle dubbed "Death rather than Humiliation," saying the campaign sought to obstruct any army attempts to capture a strategic border crossing with Jordan.

The army's control of the rebel-held crossing and swaths of territory in the southern strip of the city would sever the rebel link between the eastern and west parts of the city.