Ukraine President Volodymyr Zelenskyy on Wednesday (Ukraine time) said it was not possible to draw definitive conclusions about whether Russian forces had used chemical weapons in Mariupol.

He said it was as of now not possible to conduct a proper probe in the besieged city.

In an early-morning address, Zelenskyy said what he called repeated threats by some in Russia to use chemical weapons meant that the West needed to act now to prevent such weapons from being deployed.

He did not give details. 

The use of such potent weapons on Ukraine would constitute a serious escalation by Moscow, which is already drawing fire from the global community for targeting civilians and nonmilitary targets like train stations and hospitals for highly destructive, high-casualty strikes. World leaders including President Joe Biden have used the term "war crimes," and urged a war crimes tribunal, even before any definitive proof of chemical weapons use has been found.