Bodies of people activists say were killed by nerve gas in the Ghouta region are seen in the Duma neighbourhood of Damascus August 21, 2013 in this handout provided by Shaam News Network. Syrian activists accused President Bashar al-Assad's forces of launching a nerve gas attack on rebel-held districts near Damascus on Wednesday that they said killed more than 200 people. There was no immediate comment from Syrian authorities, who have denied using chemical weapons during the country's two-year conflict, and have accused rebels of using them, which the rebels deny. [Photo/Agencies]

AMMAN -- A Damascus opposition monitoring group said on Wednesday 494 people had been killed in a gas attack and shelling by President Bashar al-Assad's forces on Wednesday, citing data from medical centres in the Syrian capital.

Syria has denied reports of chemical weapons being used in Damascus.

The Damascus Media Office said in a statement 150 bodies were counted in Hammouriya, 100 in Kfar Batna, 67 in Saqba, 61 in Douma, 76 in Mouadamiya and 40 bodies were collected from Irbib.

"The attack began at around 3.00 am. Huge numbers of civilians were subjected to the gases. The numbers continued to increase rapidly as they suffocated to death, with lack of necessary medical supplies to save them," the statement said.