Varying reports claim that as many as 150 people were killed and more than 1,000 injured in an alleged chemical-weapons attack in the Syrian town of Douma on Saturday, perpetrated by forces loyal to Syrian President Bashar Assad.

Reports from the town northeast of Damascus were varied, with the medical-relief organization Syrian American Medical Society (SAMS) saying that 41 had been killed on April 7. The civil-defense rescue service has said that more than 150 were killed in the attacks.

A video circulated by activists shows the lifeless bodies of around a dozen men, women and children, some of them foaming at the mouth. According to SAMS, Douma hospital was targeted with a chlorine bomb, as well as a second attack of “mixed agents,” including gas.

The Syrian government has denied the launching of chemical attacks, claiming that anti-Assad rebels in Douma were close to collapse and spreading false news to obstruct the Syrian army’s advancement.

In February, Assad began winning back control of Syria’s eastern Ghouta region with the help of Russian military reinforcement in February. Douma is one of few remaining rebel strongholds in the Ghouta region.

On Friday, Assad launched a new offensive on the town, part of a deadly push which has killed more than 1,600 civilians, according to the Syrian Observatory for Human Rights.

The U.S. State Department responded on Saturday that reports of mass casualties in Douma were “horrifying,” and if confirmed, would “demand an immediate response by the international community.”

Israel has treated more than 5,000 victims of the Syrian civil war in its hospitals in the north, with another 200,000 looking to Israel for basic medical assistance.