Almost half of Kyiv’s residents were still without power as of Friday, the mayor of the Ukrainian capital said, two days after Russian strikes ravaged the country’s already ailing power grid.

“A third of houses in Kyiv already have heating, and specialists continue to restore them. Half of consumers still don’t have electricity,” said Mayor Vitali Klitschko.

“Throughout the day, energy companies plan to take turns reconnecting power to all consumers,” he wrote on Telegram as temperatures neared freezing.

The head of the national electricity company Ukrenergo, Volodymyr Kudrytskyi, said that repair work was underway across the country and that the grid had already “surmounted the most difficult phase” after the recent attacks.

Millions of Ukrainians spent Thursday without power after Russia earlier fired around 70 missiles and launched attack drones on water and electricity facilities across the country.

The systematic Russian attacks have been denounced as “war crimes” by Ukraine’s allies and follow a series of military setbacks for Russia on the front lines.

Moscow has said it only targets military-connected infrastructure, blaming Kyiv for the impact of the blackouts on civilians, saying Ukraine can end that suffering by agreeing to Russian demands.