"We have 700 people wounded in Qusair and 100 of them are being given oxygen. The town is surrounded and there's no way to bring in medical aid," said Malek Ammar, an opposition activist in the besieged town.
Rebels in Qusair sent out an appeal for support using social media outlets, saying the town near the Syrian-Lebanese border - straddling supply lines critical to both sides in Syria's civil war - could be devastated.