The deadliest chemical weapons attack in years in Syria killed dozens of people in northern Idlib province on Tuesday morning, including women and children, and sickened scores more, according to medics, rescuers and witnesses in the rebel-held province, who said the gas had been delivered by a government airstrike.

A few hours later, according to several witnesses, another airstrike hit one of the clinics treating victims, who had been farmed out to smaller hospitals and maternity wards because the area's largest hospital had been severely damaged by an airstrike two days earlier.

It was the first major atrocity attributed to the Syrian government since President Donald Trump took office. Only on Friday, administration officials stressed that ousting Syria's president, Bashar al-Assad, is no longer a priority, and that Washington's main goal is to fight the Islamic State group.

On Tuesday, the White House blamed the Syrian government for the attack, which it called a "reprehensible" act "that cannot be ignored by the civilised world", but also lashed out at the former Obama administration.