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Human rights lawyer Amal Clooney has condemned Russian President Vladimir Putin's "aggressive" war in Ukraine, saying the battered nation has become a "slaughterhouse".
Ms Clooney's remarks on Wednesday were part of an informal meeting of the UN Security Council to discuss accountability for the atrocities in the Eastern European nation.
"Ukraine is today a slaughterhouse, right in the heart of Europe," she told the gathering.
Ms Clooney said that Ukrainians had struggled to believe that Mr Putin's "outrageous" war was going to happen, despite repeated warnings from the US and earlier Russian aggression.
She said there was mounting evidence of genocide in Ukraine.
"Could it be that thousands of children are being forcibly deported to Russia?" Ms Clooney asked. "Could it be that teenage girls are being raped in the street in front of their family and their neighbours?
"Unfortunately, the answer is yes."
Moscow has repeatedly denied such allegations and says it is conducting a "special military operation" to "de-Nazify" Ukraine.
Ms Clooney said justice had been ignored for too long and the perpetrators would not be held accountable, as with Darfur and Syria, US media outlets reported.
The West has roundly condemned Russian atrocities in Ukraine, and UN humans rights chief Michelle Bachelet accused Moscow of indiscriminately shelling civilians, claims which Russia denies.
Ms Bachelet, who attended Wednesday's informal meeting, has previously said the strikes on schools, hospitals and other civilian infrastructure were evidence of war crimes.
Meanwhile, UN Secretary General Antonio Guterres is visiting Kyiv to hold discussions with Ukrainian President Volodymyr Zelenskyy.
Mr Guterres announced on Wednesday that he had arrived in the country.
On Tuesday he held talks with Mr Putin and Russian Foreign Minister Sergey Lavrov in Moscow.