BEIRUT -- Syrian activists allied with anti-government rebels alleged early Tuesday that the Syrian Army fired chemical weapons on a Damascus suburb, killing three people and injuring as many as 13.

The reports did not reference a specific time for the alleged attack, but were presented as breaking news, suggesting that they occurred late Monday or early Tuesday.

Photos and videos posted on Facebook and Twitter showed alleged victims from the town of Daraya near Damascus in a medical facility.

In the images, posted by media activists and the rebel governing council of Daraya, several men breathe through oxygen masks while some appear to suffer spasms. A tweet from the feed of the Syrian Revolution, a pro-rebel activist group that was one of groups to report the alleged attack, described their symptoms as "suffocation, short breath, and convulsion."

Shortly after reports of the attack appeared, the Twitter account of Ahmed Jarba, the president of the official Western-backed Syrian opposition, referenced the accusations.

"Barrel bombs yesterday & today poison gas killing civilians," Jarba's account read. "The culture of crimes against humanity continues."

The Syrian Coalition, which Jarba heads, did not immediately respond to a request for comment.

The report could not be independently verified, and caution was warranted: Twitter and other social media sites have emerged as crucial venues for propaganda as well as real-time reports from the battlefield dispensed by combatants, sympathizers and civilians caught in between. Doctored photos and exaggerated accounts can and have been published alongside genuine reports.

But if confirmed, the alleged attack would constitute a dramatic escalation in an already fierce civil war, following the unleashing of chemical weapons by the Syrian Army on a Damascus suburb in August.

That attack -- which contravened international treaties banning the use of chemical weapons -- brought the prospect of military reprisals from the United States and its allies. Congressional opposition put a halt to that threat, leading to a Russian-brokered diplomatic agreement under which Syria is to eliminate its chemical weapons stocks.

The United States concluded that the August attack was the handiwork of the Syrian government, accusing Assad’s regime of firing the strike on the town of Zamalka near Damascus. Under the Russian-brokered diplomatic response, ships from Western nations are currently grouping in the Mediterranean Sea to begin destruction of the chemicals.

A fresh chemical weapons attack could destroy fragile hopes for peace talks scheduled in Geneva later this month. It might well increase the likelihood of Western intervention, while reinforcing the pariah state of Assad’s government. And it could amplify support for rebel armies -- many of them extremist Islamists -- adding fuel to a war that has killed more than 100,000 people while displacing more than two million.

While the Assad government has used chemical weapons in the past, the Associated Press reported last week that rebel forces had, according to Syrian diplomatic sources, targeted government chemical weapons stockpiles for attacks.

UPDATE: 1/14 -- Chemical weapons experts told The Huffington Post that the evidence presented thus far did not suggest a chemical attack, but cautioned that information is still incomplete.

"We do think the videos are quite suspect," said Iain Thomson of SecureBio, a United Kingdom-based company that provides chemical weapons-related training and services. He said that the videos appeared to show victims who were aware of pain and voluntarily convulsing, both of which are inconsistent with agents like sarin gas. The Syrian government used sarin, a nerve agent, in its chemical weapons attack in August.

"Other, more worrying, signs and symptoms that we would expect to see from a nerve agent attack are also absent," SecureBio wrote in an analysis.