Eleven young children were among at least 58 killed in an apparent chemical weapons attack in Syria on Tuesday that was followed by the bombing of a hospital where the victims were being treated.

The Syrian regime was accused of being behind the attack in the rebel-held town of Khan Sheikhoun, which appeared to be the deadliest chemical weapons strike in the country since 2013, and left residents writhing in agony in the streets.

Hours after the poison gas canisters were first dropped, a clinic in the town was bombed by aircraft, bringing rubble and chaos down on some of the survivors and the doctors struggling to treat them.

The killings were the largest mass-scale atrocity in Syria since Donald Trump took office and came just days after his administration said that removing Bashar al-Assad from power was no longer a priority for the US. The president was under pressure on Tuesday night to clarify his position on Syria.