Zelenskiy , appearing on Tuesday via video from Ukraine, said civilians had been tortured, shot in the back of the head, thrown down wells, blown up with grenades in their apartments and crushed to death by tanks while in cars.

"They cut off limbs, cut their throats. Women were raped and killed in front of their children. Their tongues were pulled out only because their aggressor did not hear what they wanted to hear from them," he said, recounting what he described as the worst atrocities since World War II.

Over the past few days, grisly images of what appeared to be civilian massacres carried out by Russian forces in Bucha before they withdrew from the outskirts of Kyiv have caused a global outcry and led Western nations to expel scores of Moscow's diplomats and propose further sanctions, including a ban on coal imports from Russia.

Zelenskiy said both those who carried out the killings and those who gave the orders "must be brought to justice immediately for war crimes" in front of a tribunal similar to what was used in postwar Germany.

Moscow's UN ambassador, Vassily Nebenzia, said while Bucha was under Russian control, "not a single local person has suffered from any violent action."

Reiterating what the Kremlin has contended for days, he said that video footage of bodies in the streets was "a crude forgery" staged by the Ukrainians.

"You only saw what they showed you," he said.

"The only ones who would fall for this are Western dilettantes."

Associated Press journalists in Bucha have counted dozens of corpses in civilian clothes and interviewed Ukrainians who told of witnessing atrocities. Also, high-resolution satellite imagery from Maxar Technologies showed many of the bodies had been lying in the open for weeks, during the time that Russian forces were in the town.

The chief prosecutor for the International Criminal Court at The Hague opened an investigation a month ago into possible war crimes in Ukraine.

While both Ukrainian and Russian representatives sent optimistic signals following their latest round of talks a week ago, Russian Foreign Minister Sergey Lavrov said Moscow won't accept a Ukrainian demand that a prospective peace deal include an immediate pullout of troops followed by a Ukrainian referendum on the agreement.

Zelenskiy told the Security Council there was "not a single crime" that Russian troops hadn't committed in Bucha, and he likened their actions to those of the Islamic State group.

"The Russian military searched for and purposefully killed anyone who served our country. They shot and killed women outside their houses when they just tried to call someone who is alive. They killed entire families, adults and children, and they tried to burn the bodies," he said.

They used tanks to crush civilians "just for their pleasure," he said.

US Secretary of State Antony Blinken said the images from Bucha revealed "not the random act of a rogue unit" but "a deliberate campaign to kill, to torture, to rape, to commit atrocities".

He said the reports of atrocities were "more than credible".

Russia has rejected similar accusations of atrocities in the past by accusing its enemies of forging photos and video and using so-called crisis actors.

The US, in coordination with the European Union and Group of Seven nations, will roll out more sanctions against Russia on Wednesday, including a ban on all new investment in the country, a senior administration official said, speaking on condition to discuss the upcoming announcement.

But Western nations are divided over how far to go. While some are calling for a boycott of Russian oil and gas, Germany and others fear that such a move could plunge the continent into a severe economic crisis.

Australian Associated Press