President Volodymyr Zelensky of Ukraine harangued his allies to find the will to take harsher measures against Moscow, as the European Union prepared Thursday to discuss another round of sanctions and a possible ban on Russian coal.

The new sanctions would be part of the response to atrocities, including executions and torture, that appear to have been carried out by Russian forces before they retreated from areas outside Kyiv. Russia has denied responsibility, saying the atrocities were fabricated or were committed by the Ukrainians.

“Russian troops have changed their tactics and are trying to remove the killed people from the streets and basements of the occupied territory,” Mr. Zelensky said in his nightly address on Wednesday. They would not succeed in hiding evidence, he said, “because they killed a lot. Responsibility cannot be avoided.”

Europe and the United States have moved to provide more weapons to Ukraine’s military and further ostracize Russia economically with new penalties, including restrictions on its leading banks and on the assets of President Vladimir V. Putin’s children. Russia has appeared to move closer to default on its foreign debt because of U.S. currency restrictions.

The European Union is weighing a batch of sanctions that, if approved, would its harshest since the Russian invasion. The bloc is also considering a ban on coal from Russia, the leading provider of fossil-fuel energy to Europe.

Deliberations over the ban and other sanctions were set to continue into Thursday, and European Union officials and diplomats anticipated that the measures would be approved. The process reflected the challenges of reaching agreement among all 27 member nations on the penalties, which would also include banning Russian ships from E.U. ports.

NATO foreign ministers, meeting this week, have been discussing how to further help Ukraine prosecute the war without entangling the alliance in direct combat with Russian forces.

The war, they said, is far from over, noting that however badly Russia’s forces have performed, and their retreat from areas around Kyiv notwithstanding, they are making slow and brutal progress in the separatist east.

“Moscow is not giving up its ambitions in Ukraine,” said Jens Stoltenberg, NATO’s secretary general.

In other major developments:

  • Oleg Synegubov, the state administrator for the Kharkiv military region, said Wednesday in a post on Telegram that the Ukrainian army would evacuate two towns in the east because fighting was escalating there.

  • In the eastern Donetsk region, at least two people were killed and five injured when Russian forces attacked a humanitarian aid site in the town of Vugledar, according to Pavlo Kyrylenko, the Donetsk governor.

  • In the eastern Luhansk region, Russian forces now control 60 percent of the town of Rubizhne, according to the governor there, Serhiy Haidai, who said the attackers had scaled up their offensive this week.

Anushka Patil, Megan Specia, Cora Engelbrecht and Eric Schmitt contributed reporting.