April attack in Syria tied to sarin nerve agent

BEIRUT — A chemical attack in April that killed at least 84 Syrian civilians and left scores more foaming at the mouth involved sarin nerve agent, a global watchdog said Friday, days after the White House accused President Bashar Assad’s government of planning another deadly assault.

In a statement released ahead of a fuller fact-finding report, the Organization for the Prohibition of Chemical Weapons described the daybreak assault on the opposition-held town of Khan Sheikhoun as an “atrocity.”

“The perpetrators of this horrific attack must be held accountable for their crimes,” said Ahmet Uzumcu, the body’s director general.

Although the Organization for the Prohibition of Chemical Weapons said that it was not within the organization’s mandate to attribute blame for the attack, European intelligence agencies have said that samples collected in its aftermath bore the hallmarks of chemical weapons used by the Syrian government.

Images of Khan Sheikhoun’s casualties writhing in pain, many of them young children, prompted President Donald Trump to order missile strikes on the air base from which the Syrian warplanes had taken off.

This week, U.S. officials said they had observed indications that the base was being used to prepare fresh chemical attacks.

In a statement late Monday, the White House warned that Assad would pay a “heavy price” for doing so.

Chemical weapons experts say the Syrian government has used its supplies of toxic agents primarily to depopulate civilian areas and strike fear into those who remain there.

Assad’s military was supposed to have surrendered its chemical stockpiles to international inspectors in 2014. But Western diplomats and the inspectors themselves had long suspected that a portion was never declared.

Uzumcu said in a statement last month that the fact-finding team for the Organization for the Prohibition of Chemical Weapons was working to clarify “unresolved issues” over the Syrian government’s declared chemical stockpiles.

U.S. officials have monitored leadership figures and researchers from a Syrian chemical warfare unit moving between facilities linked to the production of weapons in recent weeks, according to an intelligence analyst who spoke on condition of anonymity.

The revelations indicated that Washington has monitored Syria’s chemical weapons program more closely than was publicly known.

On the morning of the April 4 attack, a network of civilian observers issued an alert as Syrian warplanes took off from the nearby Shayrat airfield and headed north to Khan Sheikhoun.

As the aircraft circled in the sky, an observer radioed colleagues to warn of an imminent attack. “Guys, tell people to wear masks,” the observer said, according to a transcript. “It has chemicals with it. I am sure of that.”