Russia came under fire Thursday accused of organising an "obscene masquerade" by bringing a group of Syrians to the OPCW to back claims that there was no chemical attack on Douma.
The group, including a young boy named Hassan Diab, testified to members of the global chemical arms watchdog in The Hague that the April 7 incident in the town had been staged.
Experts from the Organisation for the Prohibition of Chemical Weapons (OPCW) are currently in Syria to probe the alleged chlorine or sarin gas attack on Douma.
The mission was launched after gruesome footage from the apparent attack horrified the world and prompted unprecedented Western strikes on Syrian military installations.
But Syria and Russia have accused Syrian volunteer rescue workers, known as the White Helmets, of staging the video footage at the behest of the United States and its allies.
In a mounting propaganda campaign, Hassan, who is seen in the footage being hosed down and shivering, told a press conference in a hotel in The Hague that he didn't know why people began pouring water on him in the hospital.
He was among a dozen people presented as victims or doctors or hospital workers, who all told similar stories -- that someone had shouted out "chemical weapons" as hospital staff were treating injured people from a missile bombardment and panic spread.
"Unknown people started creating chaos, and pouring water on people. We were specialists and we could see there were no symptoms of the use of chemical weapons," said physician Khalil, who said he was on duty in the emergency care unit.
He said "patients with choking symptoms" had begun coming to the hospital about 7:00pm, but it "was the result of people breathing in dust and smoke" from the bombardment.
Everyone was treated and sent home, Khalil added, denying reports from the Syrian American Medical Society (SAMS) and the White Helmets who jointly said dozens of people had died.
Britain boycotted the group's earlier briefing at the OPCW, saying it was a stunt, in a move followed by France, the United States and EU countries.
"The OPCW is not a theatre. Russia's decision to misuse it is yet another Russian attempt to undermine the OPCW's work," said British ambassador to the OPCW Peter Wilson in a statement.
French ambassador Philippe Lalliot also denounced the briefing as an "obscene masquerade".
"This masquerade only betrays the huge nervousness of those who organised it and who have the most to fear from the OPCW investigation," Lalliot said.
"No-one is fooled. The truth will come out."
- 'We saw no poison' -
Hassan, who was said to be 11 years old, told dozens of journalists: "We were in the basement. We heard cries on the street that we should go to the hospital. We got scared."
"We went to the hospital through the tunnel. They started pouring water on me in the hospital I don't know why."
His father, Omar Diab, said: "The children were taken without explanation. After that we learnt it was fake. We never saw any poison or chemical agents. Neither I nor my family."
The OPCW has also criticised the meeting in its headquarters, saying it had recommended to Russia that it should wait until its inspectors had completed their work.
The White Helmets, a humanitarian organisation made up of some 3,000 volunteers, has regularly been the target of disinformation campaigns by the Syrian regime which has labelled them "terrorists".