Live Updates: U.N. Security Council to Meet as Evidence of War Crimes Mounts

“The bodies of killed people — killed Ukrainians — have already been taken from most streets, but in the yards, in the houses, the dead still remain,” Mr. Zelensky said in a translation of his remarks shared by his office. “The cities are simply ruined.”

Images of dead civilians in Bucha have prompted widespread outrage from leaders across the globe, including the European Union, which is weighing tougher penalties against Russia.

In his remarks, Mr. Zelensky said any sanctions against Russia “must finally be powerful.”

“But was it really necessary to wait for this to reject doubts and indecision?” Mr. Zelensky asked. “Did hundreds of our people really have to die in agony for some European leaders to finally understand that the Russian state deserves the most severe pressure?”

Mr. Zelensky argued in separate remarks to the Romanian Parliament on Monday that the atrocities in Bucha were made possible partly by Russia’s belief that European leadership would be weak.

He cited an editorial published the same day by RIA Novosti, the Russian state news agency, that detailed precisely how the “denazification” of Ukraine should be carried out and claimed that nearly all Ukrainians were Nazis deserving of death.

“I want you to understand me: they are not even hiding,” Mr. Zelensky said, calling the editorial evidence for future tribunals on Russian war crimes.

Mr. Zelensky said in his nightly address that the government wanted to provide journalists with “maximum access” to Bucha and other liberated regions of Ukraine.

“We are interested in having thousands of journalists there — as many as possible — for the world to see what Russia has done,” Mr. Zelensky said.

Mr. Zelensky said that information indicated that the number of victims could be even higher in other cities that have been retaken by Ukraine, such as Borodyanka, northwest of Kyiv.

“In many villages of the liberated districts of the Kyiv, Chernihiv and Sumy regions, the occupiers did things that the locals had not seen even during the Nazi occupation 80 years ago,” he said.

In cities back under the control of Ukraine, Mr. Zelensky said that the government had begun preparing to “restore normal life” by clearing areas of mines and neutralizing explosive devices, and that eventually electricity and water would be restored across the country.

“We will rebuild roads, bridges, infrastructure,” he said. “Life will come again to every city, to every community that the occupiers tried to destroy.”