As for any news (especially game-changing like this one), until it is independently verified everything must be taken with a grain of salt.

There is only one source for the claim which is Azov & it's in Mariupol where the situation is the absolute worst making it very difficult to get info & verification from another party.

What we know as of right now that plays in favor of the claim:

- Newly assigned general, Dvornikov 2 days ago, known for brutal tactics & using chemical weapons in Syria

- Head of DPR, Basurin, mention idea to use chemical weapons in Mariupol on Russian TV prior to the attack

Note: BackandAlive claims the poison used was Sarin.

Reminder: Polish President said if Russia use chemical weapons it would be "game changer", therefore a more vigorous investigation will be made before any official confirmation.