THE HAGUE, Netherlands (AP) — Russian diplomats brought alleged "witnesses" from Syria, including an 11-year-old child, to the headquarters of the global chemical weapons watchdog in the Netherlands to disprove allegations of a chemical weapons attack by the Syrian government.

The group of Syrians then held a press conference where they denied any poison gas attack took place in the town of Douma this month and said that some of them were filmed in "staged videos" in the aftermath of the April 7 suspected attack.

Russian diplomat Alexander Shulgin said the aim of the briefing was to present "evidence" that allegations of a chemical attack in Douma are "completely null and void."

"Today we can prove that the footage of the White Helmets is a crude staged action," he said, in reference to the Syrian opposition's Civil Defense group of first responders. Shulgin is Russia's ambassador to the Netherlands and representative to the global chemical weapons watchdog.

At the presser, the witnesses claimed there was no smell of chemicals, and said people who were choking had inhaled smoke and dust from a bombardment.

The press conference included testimony by an 11-year-old boy, Hassan Diab, who was seen in the aftermath of the April 7 attack being doused with water by first responders.

The boy later appeared in reports on Russian state media, in which he and his father tell Russian correspondent, Evgeny Poddubnyy, that the entire attack was staged.

The report was heavily promoted by Russia's ambassador to the United Nations, who screened it in front of the U.N. Security Council.

In the report, Diab is seen with his father speaking at what appears to be a Syrian government facility where Russian military personnel could be seen emerging from a building.

Russia had organized Thursday's briefing at the OPCW headquarters ahead of time for about 15 Syrians, including at least three young children.

The United States, France and Britain denounced the press conference as a stunt and an "obscene masquerade" by Russia. The three nations have blamed Syria for the suspected chemical attack in Douma and launched airstrikes a week later, on April 14, targeting suspected Syrian chemical weapons facilities.

"This obscene masquerade does not come as a surprise from the Syrian government, which has massacred and gassed its own people for the last seven years," said France's ambassador to the Netherlands, Philippe Lalliot.

Britain's ambassador, Peter Wilson, said he and other Western allies would not attend the briefing.

On Wednesday, OPCW inspectors made a second visit to the town of Douma, collecting samples from a new location that will be sent to designated labs for analysis. The suspected poison gas attack has sparked an ongoing clash of narratives between the West and the governments of Syria and its key ally, Russia. Damascus and Moscow insist there was no chemical weapons attack.

Opposition activists and first responders who witnessed the attack in Douma, which was under rebel control at the time, say it was carried out by government forces. Many of the victims suffocated in an underground shelter where they were hiding from government airstrikes, the activists said.

On the ground in Syria on Thursday, government forces pushed into a Damascus neighborhood held by the Islamic State group from different directions, capturing buildings on several street blocks and also tunnels used by the extremists, state media said.

State news agency SANA said dozens of IS fighters were killed in battles in the southern Damascus neighborhood of Hajar al-Aswad during which ground forces closely coordinated with the air force in bombarding the area.

The weeklong fighting in Hajar al-Aswad and the nearby Palestinian refugee camp of Yarmouk has killed dozens of people. The area is the last district out of government control in Damascus and its capture would boost security in Assad's seat of power.

The opposition's Britain-based Syrian Observatory for Human Rights said Syrian authorities ordered rebel groups in the southern Damascus suburbs of Babila, Beit Sahm and Yalda to give up their positions along fronts lines with IS in the area or face government bombardment.

The Observatory said the fighting that started last Thursday has killed 68 Syrian troops and pro-government fighters as well as 52 IS gunmen.

The U.N. agency for Palestinian refugees, UNRWA, warned of "catastrophic consequences of the severe escalation" of fighting affecting the Yarmouk refugee camp and surrounding areas.

"Yarmouk and its inhabitants have endured indescribable pain and suffering over years of conflict. We are deeply concerned about the fate of thousands of civilians, including Palestine refugees, after more than a week of dramatically increased violence", said UNRWA Commissioner-General, Pierre Krahenbuhl.

The current hostilities have caused deaths and injuries and have displaced around 5,000 civilians from Yarmouk into neighboring Yalda, of which 3,500 are Palestine refugees, UNRWA said. It added that the agency calls for the immediate granting of safe passage for civilians wishing to leave the camp and surrounding areas and for the evacuation of the injured, the sick and the elderly.

"UNRWA stands ready to provide urgently needed assistance to the population in and around Yarmouk, as soon as the security situation permits and access is granted," Krahenbuhl said.

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Associated Press writer Bassem Mroue in Beirut contributed to this report.