The Russian defence ministry on Friday accused Britain of staging a fake chemical attack in the Syrian town of Douma last weekend, a bold charge that comes amid Moscow's warnings to the West against striking Syria.

Russian defence ministry spokesperson Maj. Gen. Igor Konashenkov said that images of victims of the purported attack were fakes staged with "Britain's direct involvement," without providing evidence.

White Helmets first-responder volunteers and activists claimed an alleged chemical attack on April 7 by the Syrian government killed over 40 people in the town of Douma, drawing international outrage and prompting Washington and its allies to consider a military response. Moscow warned against any strikes and threatened to retaliate.

Says no evidence of chemical weapon use found around town or local hospital 1:59

Britain's UN Ambassador Karen Pierce rejected the charge that it was involved in staging a fake chemical weapons attack in Douma. "This is grotesque, it is a blatant lie, it is the worst piece of fake news we've yet seen from the Russian propaganda machine," Pierce told reporters Friday.

Konashenkov released statements by medics from Douma's hospital, who said a group of people toting video cameras entered the hospital, shouting that its patients were struck with chemical weapons, dousing them with water and causing panic. The medics, however, said none of the patients had any symptoms of chemical poisoning, according to the statements.

Konashenkov said that "powerful pressure from London was exerted on representatives of the so-called White Helmets to quickly stage the premeditated provocation." He added that the Russian military has proof of British involvement, but didn't immediately present it.

The accusations followed an earlier statement by Russian Foreign Minister Sergey Lavrov, who said that "intelligence agencies of a state that is now striving to spearhead a Russo-phobic campaign were involved in that fabrication." He didn't elaborate or name the state.

Attack kills dozens in Douma, but government denies involvement 1:11

When asked Friday about Russia's accusations of U.K. involvement, White House spokesperson Sarah Sanders told reporters "our intelligence tells us otherwise. I can't go beyond that."

"We have a very high confidence that Syria was responsible, and once again, Russia's failure to stop them and their continued disaction on this front has been part of the problem."

Last month Britain blamed Russia for a nerve agent attack on an ex-spy and his daughter, accusations Russia has vehemently denied.

No Trump decision

Meanwhile, U.S. Ambassador to the United Nations Nikki Haley said that Washington believes Syrian President Bashar al-Assad's forces have used chemical weapons at least 50 times during the seven-year-long conflict in his country.

"Our president has not yet made a decision about possible action in Syria. But should the United States and our allies decide to act in Syria, it will be in defence of a principle on which we all agree," Haley said Friday at an emergency meeting of the UN Security Council.

"All nations and all people will be harmed if we allow Assad to normalize the use of chemical weapons," Haley said.

A photo take April 8 shows Syrian Army soldiers gathering in an area on the eastern outskirts of Douma, as they continued their fierce offensive to retake the last opposition holdout in Eastern Ghouta. (AFP/Getty Images)

UN Secretary-General Antonio Guterres, speaking at the same meeting, said the Middle East is in such "peril" that it has become a threat to international peace and security, and Syria "represents the most serious threat."

The UN chief also said the highly volatile situation risks "escalation, fragmentation and division as far as the eye can see with profound regional and global ramifications."

The attack has drawn international outrage and prompted the United States and its allies to consider a military strike on Syria, something Moscow has strongly warned against.

In an interview with Radio-Canada earlier this week, Prime Minister Justin Trudeau said Canada is not looking to be present in Syria, which has seen years of violent, deadly conflict with no end in sight. He said Canada would, however, keep up its aid efforts and continue seeking diplomatic and political solutions.

Macron claims proof

French President Emmanuel Macron said Thursday he had proof that Assad's government was behind chlorine attacks in recent days. Syria's government denies responsibility.

On Friday, Macron stressed concerns about the deterioration of the situation in Syria in a phone call with his Russian counterpart Vladimir Putin and called for more dialogue with Moscow, his office said.

Vassily Nebenzia, Russia's ambassador to the United Nations, left, and Nikki Haley, U.S. ambassador to the United Nations, talk before a Security Council meeting on Friday at UN headquarters in New York. (Julie Jacobson/Associated Press)

U.S. Defence Secretary Jim Mattis warned Thursday that launching a military strike on Syria could spin out of control, suggesting caution in advance of a decision on how to respond to the alleged chemical weapons attack in Douma.

"Our strategy remains the same as a year ago," he said. "It is to drive this to a UN-brokered peace but, at the same time, keep our foot on the neck of ISIS until we suffocate it," referring to the Islamic State in Iraq and Syria militant group.

Mattis's remarks at a House armed services committee hearing followed a series of Trump tweets this week that initially indicated he was committed to bombing Syria but later suggested he was awaiting further advice and assessment.

Trump wrote in a Thursday morning tweet that an attack could happen "very soon or not so soon at all."

Investigators en route

A team of inspectors from the international chemical weapons watchdog is travelling to Syria to begin an investigation into the suspected chemical weapons attack.

The fact-finding mission from the Organization for the Prohibition of Chemical Weapons was expected to head to Douma, where Russia said rebels had now capitulated to government control. The Syrian government said it would facilitate the mission's investigation, which was to begin Saturday.

On Thursday, Russia's military said Douma had been brought under full control of the Syrian government under a Russia-mediated deal that secured the evacuation of the rebels and thousands of civilians after it was recaptured by Syrian forces.

The government, however, said evacuations from Douma were continuing, and no Syrian government forces had entered the town.

Douma and the sprawling eastern Ghouta region near Damascus had been under rebel control since 2012 and was a thorn in the side of Assad's government, threatening his seat of power with missiles and potential advances for years. The government's capture of Douma, the last town held by the rebels in eastern Ghouta, marked a major victory for Assad.