Ukraine’s capital Kyiv has only about half the electricity that it needs as it faces its most severe wartime energy crisis following waves of Russian attacks on its infrastructure, mayor Vitali Klitschko told Reuters on Friday.

Kyiv, one of Eastern Europe’s largest cities, requires 1,700 megawatts of electricity a day to power the services for its 3.6 million people, Klitschko said.

Klitschko said the current energy crisis was the most difficult challenge facing the capital in the nearly four years since Russia’s invasion in February 2022.

“It’s the first time in the history of our city that, in such severe frosts, most of the city was left without heating and with a huge shortage of electricity,” Klitschko, a former world heavyweight boxing champion, said in an interview in his office at the heart of Kyiv.

Klitschko said Ukraine’s international partners had rushed in additional generators, and repair teams had worked round the clock to restore heating following a Russian strike last week that knocked out supplies to 6,000 apartment buildings.

About 100 buildings still have no heating, he said.

Ukraine has declared an energy emergency this week as its grid crumbles under Russian bombardments, bitter cold temperatures and accumulated wartime damage.