Russia and Ukraine have traded almost daily assaults on each other's energy infrastructure as US-led diplomatic efforts to stop the nearly four-year war have stalled.
Elsewhere, Ukrainian Foreign Minister Andrii Sybiha accused Russia of deliberately endangering nuclear safety, as he said its mass drone and missile attack on Friday struck substations that power two nuclear power plants.
And Kremlin spokesman Dmitry Peskov said Russia intended to honour its obligations under a global nuclear test ban despite a recent order by President Vladimir Putin to study the possibility of resuming atomic tests.
A drone strike temporarily caused blackouts and cut heating to parts of Voronezh, regional governor Alexander Gusev said.
He said several drones were electronically jammed during the night over the city, home to just over a million people, sparking a fire at a local utility facility that was quickly extinguished.
Russian and Ukrainian news channels on Telegram said the strike targeted a local thermal power plant.
A missile strike late on Saturday also caused "serious damage" to power and heating systems supplying the city of Belgorod, with 20,000 households affected, local governor Vyacheslav Gladkov reported the following morning.
Russia's defence ministry said on Sunday that its forces destroyed or intercepted 44 Ukrainian drones during the night that flew over the Bryansk and Rostov regions in southwestern Russia.
The statement made no mention of either the Voronezh or Belgorod provinces, nor did it specify how many drones Ukraine launched.
Local authorities in the Rostov region on Sunday reported on hours-long blackouts in the city of Taganrog, home to about 240,000 people, blaming them on an emergency shutdown of a power line.
They did not specify the cause although local media reported a nearby transformer substation caught fire.
Months of Ukrainian long-range drone strikes on refineries have aimed to deprive Russia of the oil export revenue it needs to pursue the war.
Meanwhile, Ukraine and its allies say Russia is trying to cripple the Ukrainian power grid and deny civilians access to heat, light and running water for a fourth consecutive winter, in what Ukrainian officials call "weaponising" the biting cold.
Russia's mass drone and missile strikes on Friday hit power substations that supply two of Ukraine's nuclear power plants, Foreign Minister Sybiha said.
"Russia once again targeted substations that power the Khmelnytskyi and Rivne nuclear power plants," Sybiha said in a statement on X.
"These were not accidental but well-planned strikes. Russia is deliberately endangering nuclear safety in Europe."
Sybiha called for an urgent meeting of the International Atomic Energy Agency board of governors to respond to the risks posed by the attacks.
The people of Ukraine continue to be particularly affected by power, heating and hot water outages.
Elsewhere, Russian Foreign Minister Sergey Lavrov said he was ready to meet US Secretary of State Marco Rubio to discuss the war in Ukraine and mending bilateral ties.
"Secretary of State Marco Rubio and I understand the need for regular communication," Lavrov told Russia's Ria state agency, weeks after efforts to organise a summit between the Russian and US leaders were put on ice.
Lavrov on Sunday repeated that peace cannot be achieved without "taking Russian interests into account".
with DPA
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