Diplomats at the United Nations Security Council sparred yesterday over whether to hold President Bashar al-Assad's Government responsible for a chemical weapons attack that killed more than 80 people in northern Syria, while US intelligence officials, Doctors Without Borders and the UN health agency said evidence pointed to nerve gas exposure.
The Trump Administration and other world leaders said the Syrian Government was to blame, but Moscow, a key ally of Assad, said the assault was caused by a Syrian airstrike that hit a rebel stockpile of chemical arms.
At the UN, US Ambassador Nikki Haley warned that the Trump Administration would take action if the Security Council did not in response to the attack.
Early US assessments showed the use of chlorine gas and traces of the nerve agent sarin in the attack on Wednesday that terrorised the Syrian town of Khan Sheikhoun, according to two US officials who weren't authorised to speak publicly on the matter and demanded anonymity.
Israeli military intelligence officers also believe Syrian government forces were behind the attack, Israeli defence officials told the Associated Press. Israel believes Assad has tonnes of chemical weapons still in his arsenal, despite a concerted operation three years ago by the Organisation for the Prohibition of Chemical Weapons to rid the Government of its stockpile, according to the officials.
Turkish President Recep Tayyip Erdogan also blamed the Syrian Government for the attack.
In Khan Sheikhoun, rescue workers found terrified survivors still hiding in shelters as another wave of airstrikes battered the town yesterday. Those strikes appeared to deliver only conventional weapons damage.
Among those discovered alive were two women and a boy found hiding in a shelter beneath their home, the Civil Defence search and rescue group said.
The effects of the attack overwhelmed hospitals around the town, leading paramedics to send patients to medical facilities across rebel-held areas in northern Syria, as well as to Turkey.
The Turkish Health Ministry said three victims died receiving treatment inside its borders. The British-based Syrian Observatory for Human Rights monitoring group put the toll at 86 killed.
Victims of the attack showed signs of nerve gas exposure, the World Health Organisation and Doctors Without Borders said, including suffocation, foaming at the mouth, convulsions, constricted pupils and involuntary defecation.
Paramedics were using fire hoses to wash the chemicals from the bodies of victims.
Medical teams also reported smelling bleach on survivors of the attack, suggesting chlorine gas was also used, Doctors Without Borders said.
The magnitude of the attack was reflected in the images of the dead - children piled in heaps for burial, a father carrying his lifeless young twins.
The images from the scene were reminiscent of a 2013 nerve gas attack on the suburbs of Damascus that left hundreds dead and prompted an agreement brokered by the US and Russia to disarm Assad's chemical stockpile. Western nations blamed government forces for that attack, where effects were concentrated on opposition-held areas.
At the Vatican, Pope Francis said during his general audience that he was "watching with horror at the latest events in Syria". and that he "strongly deplored the unacceptable massacre".
Wednesday's attack happened just 100km from the Turkish border, and the Turkish Government - a close ally of Syrian rebels - set up a decontamination centre at a border crossing in the province of Hatay, where the victims were initially treated before being moved to hospitals.
At the UN, Haley, the US ambassador said there must be a response.
The US President declined to say what the US would do in response, but he did say that his "attitude toward Syria and Assad has changed very much".
"When you kill innocent children, innocent babies - babies, little babies - with a chemical gas that is so lethal, people were shocked to hear what gas it was, that crosses many, many lines," Donald Trump said in the White House Rose Garden.
The Security Council was convened in an emergency session to consider a resolution that would back an investigation by the chemical weapons watchdog into the attack and compel the Syrian Government to co-operate with a probe. It was drafted by the US, Britain and France.
Syria's Government denied it carried out any chemical attack on Khan Sheikhoun, but Russia's Defence Ministry said the toxic agents were released when a Syrian airstrike hit a rebel chemical weapons arsenal and munitions factory on the town's eastern outskirts.
British ambassador Matthew Rycroft dismissed that account, saying Britain had seen nothing that would suggest rebels "have the sort of chemical weapons that are consistent with the symptoms that we saw yesterday".
Diplomats were also meeting in Brussels for a major donors' conference on the future of Syria and the region. Representatives from 70 countries were present.
A top Syrian rebel representative said he held UN mediator Staffan De Mistura "personally responsible" for the attack. Mohammad Alloush, the rebels' chief negotiator at UN-mediated talks with the Syrian Government, said the envoy must begin labelling the Syrian Government as responsible for killing civilians. He said the UN's silence "legitimises" the strategy.
"The true solution for Syria is to put Bashar Assad, the chemical weapons user, in court, and not at the negotiations table," said Alloush, who is an official in the Islam Army rebel faction.
Syria's rebels, and the Islam Army in particular, are also accused of human rights abuses in Syria, but rights watchdogs attribute the overwhelming portion of civilian casualties over the course of the six-year war to the actions of government forces and their allies.