Russian defence ministry spokesman Igor Konashenkov says Britain told the White Helmets, who act as first responders in opposition-held areas, to fake the suspected chemical attack in the town of Douma in which at least 42 people were killed.
The Russian defence ministry on Friday said it had proof that an alleged chemical weapons attack in Syria's eastern Ghouta was staged on orders from London.
Russian Defence Ministry Spokesman Igor Konashenkov said the military had "proof that testifies to the direct participation of Britain in the organising of this provocation in eastern Ghouta."
He said Britain had told the White Helmets, who act as first responders in rebel-held areas, to fake the suspected chemical attack in the town of Douma.
London put "powerful pressure" on the civil defence organisation, Konashenkov said.
He said the attack was staged on April 7 to coincide with military action by Syrian regime forces, after the opposition group Jaish al Islam that long controlled eastern Ghouta carried out shelling of Damascus from April 3 to 6.
Russia has repeatedly accused rebels of staging or spreading rumours of chemical attacks, but the involvement of Britain is a new claim.
Moscow blamed for nerve agent attack
It comes as London has blamed Moscow for a nerve agent attack on a former double agent and his daughter in the English city of Salisbury last month.
In March, Russia's General Staff said rebels were planning a "provocation" in eastern Ghouta with women and children set to play victims of a chemical attack.
President Vladimir Putin later referred to this claim, saying on April 4 that Russia had "irrefutable proof" that opposition fighters were planning an attack with "poisonous substances".
Earlier on Friday, Russian Foreign Minister Sergey Lavrov said the suspected chemical attack was fabricated with the help of an unspecified foreign intelligence agency, without naming the country.
Lavrov also said the Russian experts have inspected the site of the alleged attack in Douma, just east of Damascus, and found no trace of chemical weapons.
He said Moscow has "irrefutable information that it was another fabrication" and that "intelligence agencies of a state that is now striving to spearhead a Russo-phobic campaign were involved in that fabrication."
Evacuations wrap up
Thousands of rebel forces and their relatives left the Syrian town of Douma they once controlled as the last evacuations from eastern Ghouta continued on Friday, a monitor said.
The rebels from the Jaish al Islam group, which fights against former Al Qaeda groups, left overnight with thousands of civilians on board 85 buses that took them to areas of northern Syria still held by the opposition.
The evacuations are part of a deal brokered by Syrian regime leader Bashar al Assad's ally Russia to re-establish regime control on eastern Ghouta, an area just on the edge of Damascus that had escaped regime control since 2012.
"After midnight, 85 buses left eastern Ghouta carrying 4,000 people, both fighters and civilians," the Syrian Observatory for Human Rights monitoring organisation said.
"Over the past few days, most of the Jaish al Islam fighters have left Douma in four successive waves," the Britain-based monitor's head, Rami Abdel Rahman, said.
The group was the last in the erstwhile besieged Ghouta enclave to resist the exit proposed by Russia but an alleged chemical attack by the regime on April 7 appeared to break their will.
The Syrian regime has consistently denied the attack and a delegation of experts from the Organisation for the Prohibition of Chemical Weapons (OPCW) chemical watchdog arrived in Damascus to investigate.
They are expected to start their work on Saturday.
"The evacuation operation should wrap up before the OPCW experts enter Douma," Abdel Rahman said.
Looking to avert war
The prospect of Western military action in Syria that could lead to a confrontation with Russia hung over the Middle East but there was no clear sign that a US-led attack was imminent.
Two days ago, US President Donald Trump warned that missiles "will be coming" in response to the suspected chemical attack.
TRT World's Kevin McAleese explains what Trump's options are.
Priority to avert war
Vassily Nebenzia, Moscow's ambassador to the United Nations, said he "cannot exclude" war between the United States and Russia.
"The immediate priority is to avert the danger of war," he told reporters.
"We hope there will be no point of no return."
Russia has warned the West against attacking Assad, who is also supported by Iran, and says there is no evidence of a chemical attack in Douma, a town near Damascus which had been held by opposition until this month.
US allies have offered strong words of support for Washington, but no clear military plans have yet emerged.
On Thursday, British Prime Minister Theresa May won backing from her senior ministers to take unspecified action with the United States and France to deter further use of chemical weapons in Syria.
Trump was also expected to speak with French President Emmanuel Macron, who said France had proof the Syrian regime carried out the Douma attack, and would decide whether to strike back when all necessary information had been gathered.
Turkey in talks with US and Russia
Turkish President Recep Tayyip Erdogan said on Friday he had discussed with his US and Russian counterparts potential steps for peace in Syria and to lighten the mood, after a series of phone calls in recent days.
Speaking to reporters, Erdogan said he had told both Trump and Putin that increasing tensions in the region was not right.
"While discussing all this, the issue we insisted on was that the increasing tensions in the region would not be right and the crisis in the region should end with the establishment of peace," Erdogan told reporters in Istanbul.
Erdogan also said the current situation showed tensions had eased, but that he would continue his talks with his US and Russian counterparts.
He also stressed the importance of opposing the use of conventional weapons in addition to chemical weapons.
"Obviously, deaths with chemical weapons are a real tragedy, a disaster, but on the other hand when barrel bombs with conventional weapons drop, they do not distinguish between people, children, women, elderly and they kill all of them mercilessly," he said.
The coalition forces especially the US and Russia need to be sensitive over the use of conventional weapons, he said.