The World Health Organization said on Monday that during the shelling of Douma "an estimated 500 patients presented to health facilities exhibited signs and symptoms consistent with exposure to toxic chemicals". The medics said none of the patients were hurt by chemicals.
The alleged attack has been denied by Syria and Russia, Assad's closest ally.
Trump made the point that it was in the national security interest to deter the production of chemical weapons.
"Maybe the regime will not use chemical weapons again, but it will not hesitate to use weapons the worldwide community has allowed it, such as barrel bombs and cluster bombs", Hariri, head of the main Syrian opposition bloc, said in a tweet.
"Insulting the President of Russian Federation is unacceptable and inadmissible", Antonov said in his statement responding to the US-led military action. "God forbid anything adventurous will be done in Syria following the Libyan and Iraqi experience", he told a news conference.
Past year on April 6, Trump ordered an attack on the Shayrat air base in central Syria.More news: Most rockets in Western attacks on Syria were intercepted: Russian Federation
"The mission of the OPCW has set off to Syria not so quickly and without abundant enthusiasm but under our and Syrian pressure", Lavrov said.
In response to Nebenzya, Haley said "I started to listen to my Russian friend and respond, but instead, I'm in awe, Vasily, of how you say what you say with a straight face".
Britain's defence ministry said "very careful scientific analysis" had been applied to maximise the destruction of stockpiled chemicals while minimising any risk of contamination to surrounding areas.
"Syrian air defence blocks American, British, French aggression on Syria", the reports said.
Syrian regime TV called the attacks a "blatant violation of global law and shows contempt for worldwide legitimacy". Assad's government controls most of the major cities, which are located in the western part of the country.
Lavrov said that "intelligence agencies of a state that is now striving to spearhead a Russo-phobic campaign were involved in that fabrication".
He did not elaborate or name the state. A US -led coalition has been conducting airstrikes in Syria since September 2014 as part of a largely successful effort to break the IS grip on both Syria and Iraq.
"We specifically identified these targets to mitigate the risk of Russian forces being involved", Dunford told reporters, adding the USA military advised Russia of airspace that would be used in the strike but did not "pre-notify them". While the United States has not been at war with the Syrian government, US troops often operate in proximity to those from Iranian- or Russian-backed groups.
He added: "We know for certain that between April 3 and April 6 the so-called White Helmets were seriously pressured from London to speed up the provocation that they were preparing".