A Syrian man receiving treatment, in Arbeen town, Damascus, Syria, on Aug. 21, 2013 (AP)
DAMASCUS, Syria (USA Today) -- Government forces loyal to President Bashar al-Assad have carried out a "poisonous gas" attack near the capital Damascus that has left hundreds dead, Syrian opposition groups claimed Wednesday.
Anti-regime activists are saying that regime forces fired "rockets with poisonous gas heads" in the attack. The number of reported deaths has ranged from 100 to close to 800. The claims and reports could not be independently confirmed.
The Syrian government said there was no truth to the allegations "whatsoever" that chemical weapons were used.
"They are an attempt to divert the United Nations commission on chemical weapons from carrying out its mission," the state-run SANA news agency said.
UN chemical weapons inspectors are in Syria this week to investigate claims that chemical weapons have been used there by both sides in a bloody and protracted civil war.
The Britain-based Syrian Observatory for Human Rights says the shelling was intense and hit the eastern suburbs of Zamalka, Arbeen and Ein Tarma. Rami Abdul-Rahman from the SOHR says he has documented at least 100 deaths from Wednesday's attack. He says it's not clear whether the victims died from shelling or toxic gas attacks.
The Local Coordination Committees said hundreds of people, perhaps as many as 775, were killed or injured in the shelling. Such different figures are common in the immediate aftermaths of attacks in Syria.
Videos and images that appeared to show victims with symptoms consistent with a chemical attack surfaced online Wednesday, although their veracity could not be immediately confirmed.
The Syrian government has long denied claims by the opposition on chemical weapons use, saying rebels fighting to overthrow Assad's government have used such weapons.
Wednesday's claim of the chemical attack, if confirmed, would be the most serious since the March 19 incident in Khan al-Assal when at least 30 people were killed. Assad's regime and the rebels have blamed each other for that attack.
Unrest in Syria began in March 2011 and later exploded into a civil war. More than 100,000 people have been killed in the conflict.
Britain's Foreign Secretary William Hague was among the first international leaders Wednesday to comment on the reports, saying he was "deeply concerned" by the allegations. The United Kingdom will raise the alleged attack with the U.N. Security. Council.
"It is clear that if they (the reports) are verified, it would mark a shocking escalation in the use of chemical weapons in Syria," Hague said.
He called on the Syrian government to allow immediate access to the area for the U.N. team currently in Syria.
France has asked the U.N. delegation to visit the site of the alleged attacks.
That request would seem to fulfill the U.N. requirement that a member state make a formal request before such action can occur. Syria would also need to agree to the request. It was not immediately clear whether that would happen.
Syria's ambassador to Russia dismissed the allegations, Russia's Interfax news agency reported.