In announcing the strikes by the US, the UK and France on three target sites in Syria suspected of either holding or producing alleged chemical weapons, Trump said he had ordered "precision strikes on targets associated with the chemical weapon capabilities" of the Syrian regime.
CNN reports the US Gen. Joseph Dunford, chairman of the Joint Chiefs of Staff, told reporters three sites were targeted: a scientific research centre in Damascus, a chemical weapons storage facility, located west of Homs, and a chemical weapons equipment storage facility and command post near Homs.
Syrian state TV said missiles targeting Homs were intercepted and did not cause damage, though CNN has been unable to verify this report.
Russia's Defence Ministry said most of the missiles fired by the US, the UK and France were shot down by Syrians using Soviet-era air defines systems, according to a report from state-sponsored Sputnik News.
Three civilians were wounded in Homs after "several" missiles were intercepted by Syria air defines systems, Syria state TV said. Witnesses on the ground in Damascus reported hearing explosions in the Syrian capital, where more than a million people live.
At a Pentagon briefing, Dunford said "this wave of airstrikes is over," but defence officials added they are prepared for a sustained campaign until the Syrian regime ceases its alleged use of chemical weapons.
Dunford said the US "specifically identified" targets to "mitigate the risk of Russian forces being involved."
He added normal communication lines were used in the run-up to the strike to ensure clearance of airspace, but said targets were not coordinated with the Russians.
The airstrike came after more than 70 people in Syria's rebel-held town of Douma reportedly died while sheltering in basements – 43 off whom showed symptoms consistent with exposure to "highly toxic chemicals," according to the World Health Organization (WHO).
The WHO, citing reports from health partners on the ground, also said that about 500 people went to the hospital showing signs of exposure to "toxic chemicals" in Douma.