Russia carried out a major overnight assault on Ukraine, which President Volodymyr Zelenskyy described on Tuesday as a breach of a commitment to refrain from targeting energy infrastructure, even as both nations prepared for discussions aimed at concluding Moscow’s four-year-long full-scale invasion.

The strikes involved hundreds of drones and a record 32 ballistic missiles, injuring at least 10 people.

Zelenskyy said the attacks were aimed at Ukraine’s power grid, part of what Kyiv describes as Moscow’s ongoing strategy to deprive civilians of electricity, heating, and running water during one of the coldest winters in recent memory.

“Exploiting the coldest days of winter to instill fear in the populace is more crucial to Russia than engaging in diplomacy,” Zelenskyy said. Overnight temperatures in Kyiv fell to minus 20 degrees Celsius, with readings of minus 16 C on Tuesday.

NATO Secretary-General Mark Rutte visited Kyiv to signal support. He said the attacks cast doubt on Moscow’s intentions ahead of the talks, calling them “a really bad signal,” and added that the assaults appear only to strengthen Ukrainian resolve.