UNITED NATIONS >> For the first time, key players seeking accountability for atrocities during the Ukraine war have come together at an informal meeting of the U.N. Security Council to spur investigations into abuses that many Western countries blame on Russia.

The session today included the International Criminal Court’s chief prosecutor, the chair of the U.N. Commission of Inquiry, Ukraine’s top prosecutor and human rights lawyer Amal Clooney.

Ukrainian Prosecutor General Iryna Venediktova, who has opened over 8,000 investigations into alleged violations of the laws and customs of war, said that “Russia’s actions amount to crimes against humanity and war crimes” and the pattern “resembles the crime of genocide.”

Albanian Foreign Minister Olta Xhacka, who co-sponsored and chaired the meeting, said that as a veto-holding member of the Security Council, Russia is supposed to be a guardian of international peace but has “embarked on a war of choice against a neighbor committing immeasurable crimes in the process.”

France’s deputy U.N. ambassador, Nathalie Broadhurst, the other co-sponsor, said the images of atrocities in the Kyiv suburb of Bucha and other areas after Russian forces withdrew “are unbearable” and may amount to war crimes.

Beth Van Schaack, the U.S. ambassador-at-large for global criminal justice, said the United States has concluded Russia committed war crimes, pointing to credible reports of individuals killed execution-style, bodies showing signs of torture and “horrific accounts of sexual violence against women and girls.” She said Russia’s political and military leadership and rank and file will be held accountable.

The legal chief at Russia’s U.N. Mission, Sergey Leonidchenko, dismissed their statements, saying: “What we heard today was another portion of unsubstantiated claims and even fakes seasoned with lies, hypocrisy and pompous rhetoric.”

Russia has denied responsibility for any atrocities and repeatedly blamed Ukrainian nationalists and “neo-Nazis.”

Leonidchenko said Ukrainians responsible for all these “heinous crimes will be brought to justice.” He said Russia is collecting witness statements and evidence across Ukraine, including in the besieged city of Mariupol. He said Russia plans to hold an informal council meeting May 6 to present what he claimed will be “facts not fakes.”

Other council members — Mexico, Gabon, Ghana, Brazil, India, Kenya and the United Arab Emirates — didn’t seek to lay any blame. They said investigations need to establish the facts behind the killings and attacks.

China, which is close to Russia, said the cause of civilian deaths should be established and verified. “Any accusations should be based on facts before the full picture is clear,” a Chinese diplomat said.

ICC prosecutor Karim Khan said a record 43 countries have referred the Ukraine situation to the court, which is responsible for prosecuting war crimes, crimes against humanity and genocide. He opened an investigation March 2, and said nine other European nations are also conducting probes. On Monday, he said, the ICC signed an agreement for the first time for a joint investigative team with Ukraine, Poland and Lithuania.

“This is a time when we need to mobilize the law and send it into battle, not on the side of Ukraine against the Russian Federation or on the side of the Russian Federation against Ukraine, but on the side of humanity to protect, to preserve, to shield people … who have certain basic rights,” Khan said.

Calling this “a critical juncture,” he said it’s time to uphold the law and move quickly on collecting evidence. He said he deployed a team to the region immediately after announcing the investigation and has visited Ukraine twice and will do so again.

Khan told the council he sent three communications to Russia and had not received a reply, and he welcomed Leonidchenko’s presence before the Russian spoke. “My door is open,” Khan told him.

Leonidchenko was critical of the ICC, claiming the court is not impartial. Khan told reporters afterward that he is not for or against Russia or Ukraine, saying the court is interested only in upholding the law.

British Ambassador Barbara Woodward said the United Kingdom “is supporting international efforts to see justice delivered” and will provide 1 million pounds ($1.25 million) in additional funding to the ICC.

France’s Broadhurst said her government has sent two judges and 10 investigators to join the ICC team in Ukraine and made an additional 500,000 euro ($525,000) contribution to support its work.

Van Schaack said the United States, which is not a party to the ICC, is supporting its investigation into atrocities in Ukraine.

Norwegian judge Erik Mose, who chairs the U.N. Human Rights Council’s Commission of Inquiry, said it is recruiting staff and will investigate all alleged violations of human rights and international humanitarian law, building on the work of U.N. human rights monitors in Ukraine. He said it will establish contact with the ICC “in the near future” and will seek to contact Russia and Ukraine, victims, civil society groups, governments and others.

“Mose stressed his commission’s independence and its mandate “to identify where possible individuals and entities responsible for violation or abuses of human rights of international humanitarian law or other related crimes.”

Michelle Bachelet, the U.N. human rights chief, reiterated that war crimes may have taken place “and efforts aimed at redressing violations must begin now.” As of today, she said, her office had documented and verified 2,787 civilians killed and 3,152 injured, with actual numbers “considerably higher” and rising.

Amal Clooney, who was representing the Clooney Foundation for Justice, urged the council not to let the efforts lose steam.

“What worries me as I sit here today is that the resolute action we’ve seen in the first 50 days of this war will turn out to be the high point instead of the starting point of the legal and diplomatic response — that your actions will slowly fade into a predictable pattern, a wealth of investigations and committees and reports and a dearth of prosecutions and convictions and sentences, politicians calling for justice but not delivering it.

“We cannot let that happen,” she said.