The US has claimed that both sarin and chlorine were used by Syria in an attack that killed dozens of civilians in Douma, an attack America, France and Britain said led them to carry out retaliatory air strikes, but which which the Syrian government denies having a role in.

On Friday night, barely an hour after the multi-nation attacks on three Syrian targets allegedly linked to the production, use and storage of chemical weapons were completed, US Defence Secretary Jim Mattis said the US was certain one deadly compound was used and that there may have been more than one. “We are not clear on that yet. We know at least one chemical agent was used,” he said.

Yet on Saturday, an unidentified US official told the media the US had now assessed that sarin and chlorine were used in the attack in the Damascus suburb of Douma.

“We do have significant information that also points to sarin use,” the official said, citing symptoms described in reporting from media, non-governmental organisations and other open sources, according to CNN. The official apparently provided no other evidence.

“Last night, operations were very successful,” said Pentagon spokesperson Dana White. “We met our objectives. We hit the sites, the heart of the chem-weapons programme. So it was mission accomplished.”

Vice President Mike Pence said the strikes, “degraded and crippled chemical weapons capabilities of Syria”.

Syrian state TV shows footage of 'destroyed scientific research centre hit by air strike'

“I think the President’s expressions this morning were a strong affirmation that the mission that he gave our military to go in and destroy key elements of the chemical weapons infrastructure in Syria was completely and professionally and swiftly accomplished,” said Mr Pence, who was on a foreign trip to Peru for the Summit of the Americas.

At the UN, US UN Ambassador Nikki Haley said she had spoken earlier in the day to Mr Trump.

“We are confident that we have crippled Syria’s chemical weapons programme. We are prepared to sustain this pressure, if the Syrian regime is foolish enough to test our will,” she said.

Syria bombings: US, UK and French military air strikes wreckage Show all 13 1 /13 Syria bombings: US, UK and French military air strikes wreckage Syria bombings: US, UK and French military air strikes wreckage The wreckage of the Scientific Studies and Research Centre in the Barzeh district, north of Damascus, which was targeted by the US, UK and France air strikes. AFP/Getty Syria bombings: US, UK and French military air strikes wreckage A Syrian soldier films the damage of the Syrian Scientific Research Center surrounded by papers and rubble. AP Syria bombings: US, UK and French military air strikes wreckage Firefighrers extinguish smoke that rises from the damage. The Pentagon says none of the missiles filed by the U.S. and its allies was deflected by Syrian air defenses, rebutting claims by the Russian and Syrian governments. AP Syria bombings: US, UK and French military air strikes wreckage The wreckage of part of the Scientific Studies and Research Centre compound . AFP/Getty Syria bombings: US, UK and French military air strikes wreckage Part of a building collapsing, surrounded by the wreckage. AFP/Getty Syria bombings: US, UK and French military air strikes wreckage Further damaged to the Scientific Studies and Research Centre compound. AFP/Getty Syria bombings: US, UK and French military air strikes wreckage Lt. Gen. Kenneth McKenzie, the director of the Joint Staff at the Pentagon, also says there also is no indication that Russian air defense systems were employed early Saturday in Syria. AP Syria bombings: US, UK and French military air strikes wreckage A Syrian soldier sprays water on the wreckage. AFP/Getty Syria bombings: US, UK and French military air strikes wreckage Syrian state news agency SANA reported several missiles hit a research centre in Barzeh, north of Damascus, "destroying a building that included scientific labs and a training centre". AFP/Getty Syria bombings: US, UK and French military air strikes wreckage A Syrian soldier films the damage. AP Syria bombings: US, UK and French military air strikes wreckage Damage to the Scientific Research Center building that was hit by the strikes. EPA Syria bombings: US, UK and French military air strikes wreckage The Scientific Studies and Research Centre was one of the targeted buildings by the US, UK and France. AFP/Getty Syria bombings: US, UK and French military air strikes wreckage Further damage to the centre. EPA

“If the Syrian regime uses this poison gas again, the United States is locked and loaded.”

Russia’s UN Ambassador Vassily Nebenzia told the council that the US and its allies struck without waiting for an investigation by the Organisation for the Prohibition of Chemical Weapons, calling the attack “hooliganism”. “This was blatant disregard for international law,” he said.

The heated words came as official from the Organisation for the Prohibition of Chemical Weapons arrived in Syria to carry out an investigation into the incident in Douma, located in eastern Ghouta where the Syrian government recently ousted the final pockets of anti-government rebels.

“The Fact-Finding Mission (FFM) team of the Organisation for the Prohibition of Chemical Weapons (OPCW) will continue its deployment to the Syrian Arab Republic to establish facts around the allegations of chemical weapons use in Douma,” the group said, adding on Twitter that its team had arrived in Damascus.