The Syrian Observatory for Human Rights on Saturday gave a breakdown of 322 people killed, including 54 children, in an alleged toxic gas attack earlier this week in a Damascus suburb,
It gave a count of "322 dead, including 54 children, 82 women and dozens of rebels, as well as 16 unidentified bodies."
Hours earlier, medical charity Doctors Without Borders (MSF) said 355 people had died after around 3,600 patients displaying "neurotoxic symptoms" flooded into three Syrian hospitals on Wednesday, the day of the alleged attacks.
The victims all arrived within less than three hours of each other, and MSF director of operations Bart Janssens said the pattern of events and the reported symptoms "strongly indicate mass exposure to a neurotoxic agent".
"Medical staff working in these facilities provided detailed information to MSF doctors regarding large numbers of patients arriving with symptoms including convulsions, excess saliva, pinpoint pupils, blurred vision and respiratory distress," he said.
Syrian opposition groups have accused President Bashar al-Assad's forces of launching massive chemical attacks near Damascus on August 21 and killing as many as 1,300 people.
The Syrian government has strongly denied those allegations, but has yet to accede to demands that UN inspectors already in the country be allowed to visit the sites.
There has been no independent verification of the number of dead, and the medical humanitarian organisation was the first independent source to report such a high toll. ram/hc