At least 58 people were killed in a suspected chemical attack in rebel-held Syrian town of Khan Sheikhun. Today’s attack caused many people to choke or faint, and some had foam coming out of their mouths, international media reports suggested.

Reports suggest that Khan Sheikhun is regularly targeted in air strikes by the government and its ally Russia, as well as the US-led multinational coalition against so-called Islamic State.

According to an Al-Jazeera report, the Britain-based Syrian Observatory for Human Rights revealed this, citing medical sources who described it as a sign of a gas attack.

Damascus has repeatedly denied using such weapons. The monitoring group, which monitors the war through a network of contacts on the ground, was unable to confirm the nature of the substance.

It is the third claim of a chemical attack in just over a week in Syria. The previous two were reported in Hama province, in an area not far from Khan Sheikhoun. If confirmed, it would be one of the deadliest chemical attacks in Syria since the civil war began six years ago.

Following the attack reports, international human rights organisation Amnesty International said the reports of the attack are alarming and must be urgently investigated.

The suspected chemical attack also highlights the failure of the international community to prevent the worst abuses in Syria’s war, and casts doubt on a signature achievement by Barack Obama, which negotiated the presumed destruction of Assad’s chemical arsenal in 2013.