The United States has formally accused Russia of using chemical weapons “as a method of warfare” against Ukraine and imposed sweeping new sanctions on Russian firms and government bodies.

In a statement on Wednesday, May 1,the US State Department said it had “made a determination that Russia has used the chemical weapon chloropicrin against Ukrainian forces in violation of the Chemical Weapons Convention (CWC).”

It added that Russia had also used “riot control agents,” or tear gas, during the war in violation of the CWC.

“The use of such chemicals is not an isolated incident, and is probably driven by Russian forces’ desire to dislodge Ukrainian forces from fortified positions and achieve tactical gains on the battlefield,” it said.

Ukrainians say they have faced increased encounters with gas and other irritant chemicals on parts of their frontline with Russia’s forces in recent months.

In a statement posted on social media in March, Ukraine’s armed forces said they had recorded more than a thousand incidents where Russia had used “tear gas munitions equipped with toxic chemicals that are prohibited for warfare,” with 250 cases in February alone.

Russia has previously denied using chemical weapons.

“There are no chemical weapons in the stockpiles of the Russian army, as confirmed by international investigations,” the Russian Embassy in the Netherlands wrote on its X (formerly known as Twitter) page, according to a report from the state-run TASS news agency in January.

Chloropicrin was widely used as a chemical warfare agent in World War I, but is no longer authorized for military use, and is now mostly used in agriculture, according to the CDC. It irritates the lungs, eyes, and skin, and can cause nausea, vomiting and diarrhea lasting for weeks, according to the CDC.

Under a 1991 law against the use of chemical and biological warfare, the State Department is “re-imposing restrictions on foreign military financing, US Government lines of credit, and export licenses for defense articles and national security-sensitive items going to Russia,” it said on Wednesday.

The State Department added that it is sanctioning three Russian government entities linked to the country’s chemical and biological weapons programs and four Russian companies that contributed to those government bodies.

The announcement was part of a tranche of nearly 300 new sanctions against companies and figures in multiple countries for their support of Russia’s war in Ukraine, including China, Azerbaijan, Belgium, Slovakia, Turkey and the United Arab Emirates.