The World Health Organization (WHO) has demanded “unhindered access” to Douma in Syria, to check reports from its partners that 500 people have been affected by a chemical attack there, the BBC reports.
The Syrian government denies being behind any use of chemical weapons.
The US has threatened a “forceful” response to reports of an attack but Russia has called this a “pretext” to attack its ally, Syria.
Russia has urged the US to avoid taking military action in response to an alleged chemical attack in Syria.
“I would once again beseech you to refrain from the plans that you’re currently developing,” Moscow’s UN envoy Vasily Nebenzia said on Tuesday.
He warned Washington that it will “bear responsibility” for any “illegal military adventure” it carries out.
The WHO cited reports that 70 people had been killed.
It said its “health cluster” partners reported that 500 people had suffered symptoms consistent with exposure to toxic chemicals, including difficulty breathing, irritation of mucous membranes, and disruption to the central nervous system.