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Russia denies that Syrian President Bashar al-Assad is to blame for a poison gas attack in Syria and said it will continue to back him, setting the Kremlin on course for its biggest diplomatic collision yet with Donald Trump's White House.
Western countries, including the United States, blamed Mr Assad's armed forces for the worst chemical attack in Syria for more than four years, which choked scores of people to death in the town of Khan Sheikhoun.
Washington said it believed the deaths were caused by sarin nerve gas dropped by Syrian aircraft, but Moscow said the poison gas belonged to rebels and had leaked from an insurgent weapons depot hit by Syrian bombs.
The United States, Britain and France have proposed a draft UN Security Council resolution that would pin the blame on Damascus but the Russian Foreign Ministry called the resolution "unacceptable".
Kremlin spokesman Dmitry Peskov said Russia would take its case blaming the rebels for the poisoning to the United Nations.
"Russia and its armed forces will continue their operations to support the anti-terrorist operations of Syria's armed forces to free the country," Mr Peskov said.
Video uploaded to social media showed civilians sprawled on the ground, some in convulsions, others lifeless. Rescue workers hosed down the limp bodies of small children, trying to wash away chemicals as people wail and pound on the chests of victims.
The charity Medecins Sans Frontieres said one of its hospitals in Syria had treated patients "with symptoms - dilated pupils, muscle spasms, involuntary defecation - consistent with exposure to neuro-toxic agents such as sarin".
The World Health Organization also said the symptoms were consistent with exposure to a nerve agent.
Turkish President Tayyip Erdogan said the attack had killed more than 100 people. That death toll could not be independently confirmed.
Hasan Haj Ali, commander of the Free Idlib Army rebel group, called the Russian statement blaming the rebels a "lie" and said rebels did not have the capability to produce nerve gas.
The incident is the first time Washington has accused Assad of using sarin since 2013, when hundreds of people died in an attack on a Damascus suburb. At that time, Washington said Assad had crossed a "red line" set by then-President Barack Obama.
Mr Obama threatened an air campaign to topple Assad but called it off at the last minute after the Syrian leader agreed to give up his chemical arsenal under a deal brokered by Moscow.
Trump described Tuesday's incident as "heinous actions by the Bashar al-Assad regime", but also faulted Mr Obama for having failed to enforce the red line four years ago.