Russian drone strikes temporarily knocked out power across Ukraine’s southern Zaporizhzhia region and left more than 600,000 households in the central Dnipropetrovsk region without electricity, Ukrainian officials said Thursday.

The bombardment came as U.S.-led diplomatic efforts continued against the backdrop of Russia’s invasion of Ukraine nearly four years earlier, with Ukraine and its Western allies working to build a framework for a possible peace settlement.

Ukrainian President Volodymyr Zelenskyy said Russia was targeting public services in the nighttime attack and criticized the effect on winter heating and power. “There is no military rationale for such strikes on energy facilities and infrastructure that leave people without electricity and heating in winter conditions,” he said on social media.

Zelenskyy also said the blackout carried no military justification and urged countries to respond to what he described as Russia’s abuse of people. He called for greater pressure on Moscow to stop its aggression, and in a post later Thursday he said there was information that “a new massive Russian attack may occur tonight.” He urged people to pay attention to air alerts in the coming days and to take shelter.

In the southern Zaporizhzhia region, the outage lasted for four hours, according to the report, and emergency crews later repaired the grid. In Dnipropetrovsk, however, officials said power had still not returned for hundreds of thousands of people by Thursday afternoon, with private energy company DTEK stating that the region remained without electricity.

The strikes highlighted Ukraine’s warning that Russia has repeatedly targeted the country’s power grid as part of what Ukrainian officials call “weaponizing winter,” including by depriving civilians of electricity, heat and running water.

Zelenskyy said the U.S. and European countries were continuing discussions on postwar rebuilding and development, and he said Ukraine has presented possible options for a peace settlement to U.S. officials who would then discuss them with Russia. “We’re waiting for a feedback on whether the enemy is truly ready to end the war,” he said.

Zelenskyy indicated that a postwar security-guarantees agreement for Ukraine with the United States was ready to be finalized, and he said it could be signed alongside U.S. President Donald Trump. He said the agreement would help deter future Russian attacks only after a peace deal is reached.

The report also said that during Thursday, Russia launched two ballistic missiles on Kryvyi Rih, hitting apartment buildings and injuring 10 people, with one man in critical condition, according to Oleksandr Vikul, head of the regional military administration.

Separately, the Russian Defense Ministry said air defenses downed 66 Ukrainian drones overnight over Russian regions, the illegally annexed Crimea, the Black Sea and the Azov Sea.