Did Russia really use chemical weapons in Ukraine? Experts remain sceptical

Analysis: Little evidence thus far that civilians in Mariupol had fallen ill because of chemical attack

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• What we know on day 48 of the invasion

An initial report circulating on Monday night from Ukraine said Russian forces had used a poisonous substance of unknown origin" against Ukrainian civilians and military holed up in the besieged city of Mariupol.

The victims were described as having respiratory failure" and a rather specific diagnosis of vestibulo-atactic syndrome", nominally inner ear problems leading to dizziness and perhaps vomiting, eye twitching and loss of balance.