Failaq al-Rahman rebel group says attack caused suffocation to more than 30 people. Regime forces dismiss the attack as fabrication.
A Syrian rebel group accused the Syrian regime of using chlorine gas against its fighters on Saturday in battles east of Damascus - an allegation the regime forces swiftly denied as fabrication.
The Failaq al-Rahman group said that more than 30 people suffered suffocation as a result of the attack in Ain Tarma in the eastern Ghouta region, which the regime forces have been battling to take back from insurgents.
"The gas attack has been conducted by artillery fire," Waiel Olwan, spokesman of the group, told Anadolu Agency.
In a statement circulated by state-run media, a regime source said that the army command completely denied the accusation. "It has not used any chemical weapons in the past, and will not use them at any time".
The US said on Wednesday said that the Syrian regime leader Bashar al Assad appeared so far to have heeded a warning issued earlier in the week not to carry out a chemical weapons attack after saying it saw possible preparations for one.
Regime denies role in April chemical attack
Western governments including the US say that the Syrian regime was behind an April gas attack in the town of Khan Shaykhun that killed dozens. In response, the US fired cruise missiles at the air base from which it said the attack was launched.
The Syrian regime has denied any role in that attack.
On Saturday the regime also dismissed a report by the international chemical weapons watchdog that said the banned nerve agent sarin was used in the April attack, saying it lacked "any credibility".
"The report comes up with a fabricated and exaggerated story that has no credibility and can't be accepted in any way because it is illogical and is the creation of a sick mind," the regime foreign ministry said.
The findings by the Organisation for the Prohibition of Chemical Weapons (OPCW) will now be taken up by a joint UN-OPCW panel to determine whether Syrian regime forces were behind the attack.
"Based on its work, the FFM (fact-finding mission) is able to conclude that a large number of people, some of whom died, were exposed to sarin or a sarin-like substance," said the report.
The OPCW-UN joint investigative mechanism (JIM) has already determined that Syrian regime forces were responsible for chlorine attacks on three villages in 2014 and 2015, and that Daesh used mustard gas in 2015.
Russia, Syria's ally, has dismissed the findings as not credible. In February, Moscow vetoed a UN resolution that would have imposed sanctions on Syria over chemical weapons use in the six-year war.
Separately, Assad regime forces on Saturday afternoon launched an artillery attack in west-central Hama province on civil defense center of the White Helmets -- a volunteer rescue group established in 2014 operating in Syria's opposition-held areas, the group announced on its Twitter account. The building was largely damaged as two rescue vehicles were totally destroyed, according to the civil defense group.