The Russian Defense Ministry claimed a drone attack on the positions of Russian troops in Ukraine using toxic substances, TASS reported on Saturday, citing Lieutenant-General Igor Kirillov.

"On April 21, 2022, a container with ampoules was dropped onto the position of the Russian troops from a UAV. It was planned that when they were destroyed, a chemical reaction would occur that would cause an explosion and fire with the release of toxic substances not included in the conventional lists," Kirillov said.

The Russian Defense Ministry also claimed the U.S. was preparing provocations to accuse the Russian military of using chemical, biological or nuclear weapons in Ukraine. 

According to the Russian military, the most likely option is a provocation at chemical and biological facilities in Kharkiv and Kyiv, and a provocation at the Zaporizhzhia nuclear power plant is not ruled out. 

There is no response from the Ukrainian side yet.