'Horrific' footage
The BBC's Middle East Editor Jeremy Bowen says many will ask why the government would want to use such weapons at a time when inspectors are in the country and the military has been doing well militarily in the area around Damascus.
Some will suspect that the footage has been fabricated, but the videos that have been emerged would be difficult to fake, he adds.
Prof Alexander Kekule, of the Institute for Medical Microbiology at Halle University in Germany, told the BBC that one of the videos - although of poor quality - was consistent with the aftermath of an attack with a chemical agent.
But he added that none of the patients showed typical signs of sarin or other organophosphorous nerve agents, or signs of blistering agents.
"It also cannot be totally excluded that the whole video is a political staging. In this case, however, it would be a very good one," he said.
"Taken together, the best guess is that this is an authentic video of the aftermath of an attack with some incapacitating chemical agent."
Both the rebels and government forces have accused each other of using chemical weapons during the conflict.
It has not been possible to independently verify the claims.
In July 2012, the Syrian government implicitly admitted what had long been suspected - that Syria had stocks of chemical weapons.
Experts believe the country has large undeclared stockpiles of mustard gas and sarin nerve agent.
Damascus said the weapons, stored and secured by the armed forces, would never be used "inside Syria", but could be used against an external attack
http://www.bbc.co.uk/news/world-middle-east-23777201
