BEIRUT - Rescue workers in a Syrian rebel-held enclave east of Damascus accused government forces of using chlorine gas during bombardment of the area on Monday, and the Syrian Observatory for Human Rights said at least 13 people had suffered suffocation.The Syrian army and government have consistently denied using chlorine or other chemical weapons during Syria's conflict, now in its seventh year.The White Helmets civil defense rescue force, which operates in rebel-held parts of Syria, said 13 civilians including women and children had been "injured after (the) Assad regime used Chlorine gas in Douma city in EasternGhouta."Douma is in the eastern Ghouta, a suburb east of Damascus where almost 400,000 people have been under siege by the Syrian government and allied militia since 2013. Eastern Ghouta is the last major rebel position close to the capital.The health directorate for opposition-held areas in the Damascus region said patient symptoms "suggest they have been exposed to chlorine gas inhalation."It said patients said the smell around the attack site resembled chlorine.The Britain-based Syrian Observatory for Human Rights, quoting local medical and other sources, said "gasses" released during a dawn rocket attack on Douma city caused "cases of suffocation."The Observatory said a gas was also used during a rocket attack last week on the enclave.A witness in the area said people had fled the area of the attack and were receiving treatment for breathing problems at medical centers.In the past two years, a joint UN and the Organization for the Prohibition of Chemical Weapons (OPCW) inquiry has found the Syrian government used the nerve agent sarin and has also several times used chlorine as a weapon.It has also said Islamic State has used sulfur mustard.