A Syrian opposition news outlet claimed Friday the government troops attacked a Damascus suburb with poison gas and that residents were showing symptoms of shortness of breath, Alarabiya reported.
The Shaam News Network identified the Damascus suburb of Harasta as the site of the poison gas attack and said that at least 100 residents were critical condition.
The opposition Syrian Coalition issued a statement condemning the alleged attack using "poison gas and highly concentrated pesticides."
"Assad is dragging his feet over the elimination of the chemical weapons arsenal, missing a series of deadlines while at the same time spraying people with gas on a scale- he thinks- small enough to avoid world condemnation," said Badr Jamous, Syrian Coalition Secretary General, in the statement.
"The international community has a moral duty to voice its rejection of this crime and indeed take immediate firm steps to restrain a regime that is prepared to use all kinds of conventional and unconventional weapons to cling to power," Jamous added.
Responding to a question, White House spokesman Jay Carney said the U.S. was working with the Organization for the Prohibition of Chemical Weapons (OPCW) to check on whether the Syrian government was abiding to the 2013 deal on the destruction of Syria's chemical weapons stockpile.
Members of the Syrian opposition have in recent months accused President Bashar Assad's regime of using chemical arms in a number of attacks including in the two Damascus suburbs of Harasta and Jobar.
U.S. and British officials are reportedly investigating claims that Assad's forces have used chemical weapons in at least four attacks around Damascus between January and April.
The London Times Friday cited British officials as saying that they were "aware of multiple allegations" of poison gas attacks against opposition forces on the outskirts of the capital.
The Times reported that the regime this time may have been using "toxic industrial substances" to frighten rebels in a way that does not trigger a wide international outcry.
This week an Israeli defense official said Assad had used chemical weapons again around the capital at the end of March. The Times of Israel reported that "the nonlethal agents were used to incapacitate opposition fighters."
It cited the defense official as saying that one attack occurred on March 27 in the capital's Harasta neighborhood, and that "the effects of the chemicals lasted for several hours."
In December, a U.N. inquiry found that Sarin gas had likely been used in Jobar and another Damascus suburb called Ghouta. The Syrian opposition accused the Syrian government for the attacks but the regime denied the allegations.
Outrage over the Aug. 21 Ghouta attack, were hundreds of people were killed, sparked global outrage as well a U.S. threat of military strikes.
The strikes were dropped after Damascus vowed to destroy is chemical weapons stockpile, a process that is being supervised by the OPCW.
Any use of chemical weapons by the Syrian regime would be in clear breach of the agreement it signed with the OPCW.