Syrian rebels in Aleppo
Syrian rebels in AleppoReuters

Syrian opposition activists on Thursday accused President Bashar Al-Assad's forces of once again using poison gas in Syria's civil war, a charge denied by the Syrian government.

Reuters quoted the opposition as having said victims of the alleged attack had been discovered with swollen limbs and foaming at the mouth.

The activists said that two shells loaded with gas hit a rebel-held area in the town of Nabak, some 68 kilometers (40 miles) northeast of Damascus, on a major highway in the Qalamoun region. They reported seven casualties.

Separately, the Syrian Revolution Coordinators Union also accused Assad's forces of using poison gas.

"We have documented nine casualties from poison gas used by the regime in neighborhoods of Nabak," it was quoted as having said on its Facebook page.

"Seven men are reported ill so far. They have swollen limbs and foam coming out of their mouths," an activist calling himself Amer al-Qalamouni told Reuters.

"No doctors have got to them yet because Nabak is under ferocious bombardment and there are very few medical staff left," he added.

Responding to the claims, the Syrian government called them “an impudent lie” and said they were an attempt by the rebels to recoup themselves for their defeat in the battlefield, reported Voice of Russia.

Asked about the latest incident, a U.S. official in Washington told Reuters, "We have seen the reports, but have no confirmation."

The reports about another chemical attack come as the Organization for the Prohibition of Chemical Weapons (OPCW) is hard at work destroying Syria’s chemical weapons arsenal, in accordance with a plan agreed upon by the United States and Russia.

The U.S.-Russia effort was a last-minute measure to prevent an American strike on Syria in retaliation for the regime's alleged use of chemical weapons in a previous attack in August that left hundreds dead.

While Syria has won praise for cooperating with the mission, it was recently reported that the United States is looking at new classified intelligence indicating that the Syrian government may not fully declare its chemical weapons stockpile.

This would mean that Syria will still have a secret cache of chemical weapons even after the current agreed-upon destruction effort is carried out.

A former Syrian general has warned that President Bashar Al-Assad prepared for the chemical weapons crackdown in advance by hiding his weapons stockpile with the Lebanese group Hezbollah, a close ally.