The United States accused Russia of using a UN Security Council meeting Friday for “lying and spreading disinformation” as part of a potential false-flag operation by Moscow for the use of chemical or biological agents in Ukraine.

US Ambassador Linda Thomas-Greenfield said Russia was playing out a scenario put forth in the council last month by US Secretary of State Antony Blinken — that President Vladimir Putin would “fabricate allegations about chemical or biological weapons to justify its own violent attacks against the Ukrainian people.”

“The intent behind these lies seems clear, and is deeply troubling,” she said. “We believe Russia could use chemical or biological agents for assassinations, as part of a staged or false-flag incident, or to support tactical military operations.”

The United States has warned about such Russian operations in conjunction with an invasion, which began Feb. 24.

Russia had requested the meeting to address its allegations of US “biological activities” in Ukraine — a charge made without any evidence and denied by both Washington and Kyiv.

Russia’s UN Ambassador Vassily Nebenzia said its Defense Ministry had documents charging that Ukraine has at least 30 biological laboratories carrying out “very dangerous biological experiments” involving pathogens, and its work “is being done and funded and supervised by the Defense Threat Reduction Agency of the United States.”

Ukraine does have a network of biological labs that have gotten funding and research support from the US — but they are owned and operated by Ukraine and are part of an initiative called the Biological Threat Reduction Programme that aims to reduce the likelihood of deadly outbreaks, whether natural or manmade.

The US efforts date back to work in the 1990s to dismantle the former Soviet Union’s program for weapons of mass destruction. “The labs are not secret,” said Filippa Lentzos, a senior lecturer in science and international security at King’s College London, in an email to the Associated Press.

“They are not being used in relation to bioweapons. This is all disinformation.” Britain’s UN Ambassador Barbara Woodward, called the allegations “utter nonsense” and said “Russia is sinking to new depths today, but the council must not get dragged down with it.”

UN disarmament chief Izumi Nakamitsu told the council she was aware of media reports about the allegations of and said: “The United Nations is not aware of any biological weapons programs.” Thomas-Greenfield also denied that Ukraine has a biological weapons program or biological weapons labs as Russia claimed, saying the public health laboratory facilities are used to detect and diagnose diseases like Covid-19, with US help.

Thomas-Greenfield said that ever since Russia began building up forces near Ukraine’s borders, Washington’s strategy has been to counter Moscow’ tactics and share what it knows with the world. “We’re not going to let Russia get away with lying to the world or staining the integrity of the Security Council by using it as a venue for legitimizing Putin’s violence,” she said. She accused Russia’s ally, China, of “spreading disinformation in support of Russia’s outrageous claims.”

China’s UN Ambassador Zhang Jun expressed concern at Russia’s accusations and urged an investigation to “provide a comprehensive clarification and accept a multilateral verification.”

Britain’s Woodward said the Security Council must not be “an audience for Russia’s domestic propaganda” and must remain focused on Russia’s invasion of Ukraine.

“We should not allow Russia to abuse its permanent seat to spread disinformation and lies and pervert the purpose of the Security Council,” Woodward said.

Ukraine’s UN Ambassador Sergiy Kyslytsya said Moscow’s accusations “may actually point at Russia preparing another horrific false-flag operation.”

Noting that Russia has already used cruise missiles, multiple rocket launchers and heavy aerial bombardment, he addressed Putin by asking: “So what else are you going to use against Ukraine?” The UN human rights office, meanwhile, has received “credible reports” that Russian forces are using cluster munitions in Ukraine, including in populated areas which is prohibited under international humanitarian law, Undersecretary-General Rosemary DiCarlo told the Security Council.

“Indiscriminate attacks, including those using cluster munitions, which are of a nature to strike military objectives and civilians or civilian objects without distinction, are prohibited under international humanitarian law,” DiCarlo said.

“Directing attacks against civilian and civilian objects, as well as so-called area bombardment in towns and villages, are also prohibited under international law and may amount to war crimes.” Nebenzia replied that the allegations are “refuted repeatedly by our Ministry of Defense.” The Russian request for the Security Council meeting came from its first deputy UN ambassador, Dmitry Polyansky.

Russian Foreign Ministry spokeswoman Maria Zakharova had made the accusation earlier this week. White House press secretary Jen Psaki called Russia’s claim “preposterous” and tweeted: “This is all an obvious ploy by Russia to try to justify its further premeditated, unprovoked, and unjustified attack on Ukraine.” Ukrainian President Volodymyr Zelenskyy also denied Russia’s accusation, saying the accusation itself was a bad sign.