The governor of Russia's Belgorod region, which borders Ukraine, said on Saturday that 600,000 residents were without electricity, heating and water after a Ukrainian missile strike.
In a statement posted on Telegram, Vyacheslav Gladkov said that work was underway to restore supplies, but that the situation was "extremely challenging".
Footage filmed by Reuters in Belgorod city showed streetlights extinguished and locals finding their way using hand-held torches and car headlights.
Belgorod region, which adjoins Ukraine's Kharkiv region and had a pre-war population of 1.5 million, has come under regular attack from Kyiv's forces since Russia ordered tens of thousands of troops into Ukraine in February 2022.
Russia has frequently bombarded Ukraine's power infrastructure, causing rolling daily blackouts, and has also targeted heating systems this winter. An overnight strike on Thursday left about half of Kyiv's apartment blocks without heat.
Temperatures in most of Russia and Ukraine have been well below freezing in recent days.
