Volodymyr Zelenskyy
Volodymyr Zelenskyy Reuters

Ukrainian President Volodymyr Zelenskyy said on Monday that Russia could use chemical weapons in Ukraine and called on the West to impose strong sanctions on Moscow that would deter even talk of the use of such weapons, Reuters reported.

His comments followed unconfirmed reports suggesting that chemical weapons were used in the besieged southern Ukrainian port of Mariupol.

"We treat this with the utmost seriousness," Zelenskyy said late on Monday. He did not say chemical weapons had already been used.

"I would like to remind world leaders that the possible use of chemical weapons by the Russian military has already been discussed. And already at that time it meant that it was necessary to react to the Russian aggression much harsher and faster," he added.

Petro Andryushchenko, an aide to the mayor of Mariupol, wrote on his Telegram channel reports about a chemical attack had not been confirmed and that he expected to provide details and clarifications later.

Russia recently claimed that Ukraine is running chemical and biological labs with US support.

White House press secretary Jen Psaki later rejected the claims from Russia as "false" and "preposterous," and warned they could serve as a pretext for the Russians to deploy chemical weapons in their assault on Ukraine.

US President Joe Biden then said that Russian accusations that Kyiv has biological and chemical weapons are false and illustrate that Russian President Vladimir Putin is considering using them himself against Ukraine.

Zelenskyy also insisted that no chemical weapons or other weapons of mass destruction were developed in his country.

"No chemical or any other weapons of mass destruction were developed on my land. The whole world knows that. You know that. And if Russia do something like that against us, it will get the most severe sanctions response," he said.