Russian airstrikes targeted the main hospital of Dael in southern Daraa on Saturday night, killing and wounding medics and patients and forcing services to stop, local activists said.
The vacuum missiles attack on the medical facility comes as rebels made gains against regime forces and allied militias in the Old City of Daraa.
Most hospitals in rebel-held areas are not in service due to a lack of equipment and deliberate targeting by the Assad regime.
Since rebels launched a major offensive in early February, they have managed to capture the heavily populated Manshiya district and a number of regime bastions in the border province.