Medecins Sans Frontieres says it has treated about 3,600 patients in Damascus with "neurotoxic symptons". Of that number, 355 have died, AFP reported.
The charity said patients started arriving on August 21, the same day the opposition claims chemical attacks were made by the Syrian military against rebels.
Symptoms of patients included convulsions, extreme salivation, contracted pupils and respiratory problems, according to the BBC. Patients were being treated with atropine, MSF said.
The news come on the same day the Syrian government accused rebels of orchestrating the alleged chemical weapons attacks, as well as that that a top UN official arrived in Damascus to push forward chemical inspectors' entry to sites where people have died.
