The US warned Wednesday of the potential for Russia to use chemical or biological weapons in Ukraine, saying the United States does not “possess such weapons anywhere.”

In a series of tweets, White House spokeswoman Jen Psaki said Russia falsely claimed that the US has biological weapons labs and chemical weapons development facilities in Ukraine, claims which she said were echoed by Chinese officials.

"This is preposterous," said Psaki, adding that "It’s the kind of disinformation operation we’ve seen repeatedly from the Russians over the years in Ukraine and in other countries, which have been debunked, and an example of the types of false pretexts we have been warning the Russians would invent.”

"Now that Russia has made these false claims and China has seemingly endorsed this propaganda, we should all be on the lookout for Russia to possibly use chemical or biological weapons in Ukraine, or to create a false flag operation using them. It’s a clear pattern," Psaki wrote.

The warning comes in response to claims by Russian Foreign Ministry spokeswoman Maria Zakharova, who said that documents suggest "components of bioweapons were being developed in Ukraine."

Speaking at a weekly briefing in Moscow, Zakharova said the Russian Armed Forces received evidence of the development of biological weapon components by Ukraine under US guidance from the employees of Ukraine's biological labs.

Psaki said the US is in full compliance with its obligations under the Chemical Weapons Convention and the Biological Weapons Convention, adding Washington "does not develop or possess such weapons anywhere."

She accused Russia of having "a long and well-documented track record" of using chemical weapons, citing the poisoning of Russian President Vladimir Putin’s political rival Alexey Navalny.

Psaki also cited the war in Syria, accusing Moscow of using chemical weapons to support the Bashar al-Assad regime.

"It’s Russia that has long maintained a biological weapons program in violation of international law.”

She noted that Russia had accused the West in the past of the "very violations that Russia itself is perpetrating" and recalled that in December, Moscow falsely accused Washington of deploying contractors with chemical weapons in Ukraine.

"This is all an obvious ploy by Russia to try to justify its further premeditated, unprovoked, and unjustified attack on Ukraine," she added.

The Russia-Ukraine war, which started on Feb. 24, has drawn international condemnation, led to financial sanctions on Moscow and spurred an exodus of global firms from Russia, including McDonald's and Starbucks over the last 24 hours.

At least 516 civilians have been killed and 908 others injured in Ukraine since Russia launched the war against its neighbor, according to UN figures, with the real toll feared to be higher.

More than 2.1 million people have fled Ukraine to neighboring countries, according to the UN Refugee Agency. (Anadolu Agency)

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