Raging at Russia over growing evidence of atrocities, President Volodymyr Zelensky of Ukraine on Tuesday delivered one of his most forceful denunciations of the invasion in a live video speech to the United Nations Security Council, calling the Russians war criminals who he said had killed families, raped women in front of their children, pillaged homes and left his country in ruins, “filled with mass graves.”
In his speech — a day after touring Bucha, a suburb of Kyiv, the capital, where images have surfaced of many bodies of civilians Mr. Zelensky said had been killed by retreating Russian troops — the Ukrainian president said the Security Council was useless if it could not find a way to hold the perpetrators to account.
“There is not a single crime that they would not commit there,” Mr. Zelensky said of the departed Russian troops.
“Now the world can see what the Russian military did in Bucha, but the world has yet to see what it has done in other parts of our country,” Mr. Zelensky said.
“Where is the security that the Security Council needs to guarantee?” he asked. “It’s not there.”
Much of his speech was laced with frustration with the United Nations for having failed to avert the war by not enforcing basic principles of the organization’s founding charter.
“Show how we can reform and work for peace,” Mr. Zelensky implored council members. Otherwise, he said, “dissolve yourself altogether, if there is nothing you can do besides conversation.”
Mr. Zelensky also called for the creation of a tribunal that would prosecute the Russians he said were responsible for the atrocities, including leaders in Moscow, drawing an analogy to the Nuremberg court that tried Nazi war criminals.
The Kremlin has denied any responsibility for the civilian atrocities in Bucha or elsewhere in Ukraine and has said the photographs and visual evidence of execution-style killings in the northern suburbs are fabrications.
An analysis of satellite images by The New York Times rebuts claims by Russia that the killing of civilians in Bucha occurred after its soldiers had left the town.
“They purposely killed anyone,” Mr. Zelensky said. “They killed entire families, adults and children, and they tried to burn the bodies.”
Some victims in Bucha were “shot and killed in the back of their heads,” he said, while “some were shot on the street, others thrown into wells.”
It was Mr. Zelensky’s first speech to the Security Council since the invasion more than a month ago, and he showed no sign of wishing to negotiate with Russia. Rather, he described the United Nations as a powerless and outdated organization that needed to purge Russia of the veto power it wields on the council.
Afterward, the council viewed a short video supplied by the Ukraine government that showed images of what appeared to be charred, rotting and slaughtered bodies from several Ukrainian cities.
Barbara Woodward, the British ambassador who is the council’s president for April, described the images as harrowing. “Speaking in my national capacity, we are appalled by what we have seen and reiterate our solidarity with Ukraine,” she said, a sentiment echoed by several other ambassadors.
Russia’s ambassador, Vasily Nebenzya, categorically rejected all of Mr. Zelensky’s accusations and said Russian forces could not have possibly committed such acts.
He suggested the Ukrainian leader had been deceived by the United States and its European allies. He also suggested that neo-Nazis controlled the Ukrainian government, invoking a false narrative that Russia has used to justify the invasion of the former Soviet republic.
Nazis, Mr. Nebenzya said, “are running the show” in Ukraine. “How can it be any other way when the people running Ukraine are Nazi collaborators?”
Addressing Mr. Zelensky, the Russian ambassador said: “You simply prefer not to notice Ukrainian Nazis, pretending they’re not there. Unfortunately, they are there.”
Mr. Zelensky, who is Jewish, lost many family members in the Holocaust.
The Security Council meeting, which was called by Western members to discuss the atrocities uncovered this weekend, did not appear to shift any positions on the 15-member body, the most powerful in the U.N. system.
Russia, one of the five veto-wielding permanent members, has long made clear it would block any measure that ascribes blame or responsibility for the war to Russia. It has found a supportive ally in China, which has said Russian grievances are legitimate and that peaceful negotiations are the only solution.
China’s ambassador, Zhang Jun, said the images from Bucha were disturbing but that accusations should not be launched at any side until an independent investigation established the facts. “Humanitarian issues should not be politicized,” said Mr. Zhang. “International aid agencies should maintain neutrality and impartiality.”