Chemical weapons inspectors have not yet been allowed access to Syria’s Douma, UK officials said as the Organisation for the Prohibition of Chemical Weapons (OPCW) met to discuss the “alleged use of chemical weapons” in Syria.

“Russia and Syria have not yet allowed access to Douma,” the British delegation tweeted on Sunday, adding that “unfettered access [is] essential” and “Russia and Syria must cooperate”.

Russian Deputy Foreign Minister Sergei Ryabkov immediately denied the allegations that inspectors were not being allowed access, according to Russian news agency RIA.

He said the arrival of the inspectors were delayed as a result of the US-led air raids on Saturday.

Syrian Deputy Foreign Minister Faisal al-Mokdad confirmed that government officials had met OPCW inspectors, according to Syrian state news agency SANA.

“The experts have been in Syria for the past three days upon the request of the Syrian government and several meetings were held during which the cooperation between the two sides was discussed,” SANA quoted al-Mokdad as saying.

The OPCW, an intergovenmental organisation that oversees the implementation of the Chemical Weapons Convention, met delegates in The Hague on Monday to discuss events surrounding the April 7 attack in Douma.

Syrian government forces retook Douma last week, gaining full control over the former rebel-held enclave of Eastern Ghouta, Russian military officials announced at the time.

The announcement came just days after dozens people were killed by alleged chemical weapons attack in the town, sparking international outcry and prompting the US, UK and France to launch missile attacks on facilities believed to be used to research, develop and store chemical weapons inside Syria.

The Chemical Weapons Convention outlaws the production or stockpiling of chemical weapons.

Syria is a signatory of the treaty. Egypt, Israel, North Korea and South Sudan are the only nonsignatory nations.

‘Barbaric use of chemical weapons’

Peter Wilson, the UK’s OPCW envoy, told the watchdog body that failure to act in Syria will cause “further barbaric use of chemical weapons.

Syria has lived through a seven-year civil war that has killed at least half a million people and created an international refugee crisis.

“The Syrian Regime has an abhorrent record of using chemical weapons against its own people. Chemical weapons use has become an all too regular weapon of war in the Syrian conflict,” Wilson said, going on to cite 390 allegations of chemical weapons attacks since 2014.

Russia has impeded international bodies from investigating these attacks, Wilson added.

Russia told the UN last Friday that its experts found no trace of “toxic substance use” during their investigation in Douma.

Vassily Nebenzia, Russia’s UN ambassador, said Russia has “clear evidence” that the chemical attack was staged.

For its part, France has said it has evidence Russia was responsible.

US Ambassador to the UN Nikki Haley has said her country will announce new sanctionson the Russian government in response to its support for Syria’s Bashar al-Assad.