A White House official says the United States believes it is "extremely unlikely" that Turkey used chemical weapons against Kurds during its military campaign in the Afrin Province of northern Syria.
The official said on February 17 that U.S. officials were aware of the reports but had no evidence to confirm them.
The U.S. comments come after claims by the head of Afrin hospital in northern Syria that six men were treated late on February 16 after shelling and had symptoms that appeared to indicate exposure to toxic agents, including "enlarged pupils" and "breathing difficulties."
The claims could not be independently verified. Videos from the hospital showed people being fitted with oxygen masks but who did not otherwise show symptoms of a chemical attack.
Turkey on January 19 began an air-and-land military campaign in the Kurdish-controlled Afrin enclave in northern Syria, saying it was targeting Kurdish terrorists.
The alleged use of chemical weapons in the seven-year civil war in Syria has long been an issue, with the United Nations previously declaring evidence of use by President Bashar al-Assad in his fight against rebels.
U.S. national security adviser H.R. McMaster, speaking at the Munich Security Conference on February 17, said public reports "clearly show" that Assad's forces are continuing to use chemical weapons.
Assad's government rejects accusations that it deploys chemical weapons.
The United States and Turkey support differing rebel groups fighting the Syrian government, while Russia and Iran back Assad’s government in the war.