Ukraine has warned there would be emergency blackouts once again in several regions as it repaired damage from missile attacks, while Moscow has accused Kyiv of attacking deep inside Russia with drones.
A new Russian missile barrage had been anticipated in Ukraine for days and it took place over the last 24 hours just as emergency blackouts were due to end, with previous damage repaired.
The strikes, which plunged parts of Ukraine back into freezing darkness with temperatures below zero were the latest in weeks of attacks hitting critical infrastructure and cutting off heat and water to many.
At least four people were killed, Ukrainian President Volodymyr Zelenskiy said, adding that most of some 70 missiles were shot down.
"In many regions, there will have to be emergency blackouts," he said in a late Monday video address. "We will be doing everything to restore stability."
About half the region surrounding the Ukrainian capital will remain without electricity for the coming days after Russian missile strikes on power facilities, the Kyiv regional governor Oleksiy Kuleba said on Telegram.
The region around the capital has a population of 1.8 million.
The United States said it would convene a virtual meeting on Thursday with oil and gas executives to discuss how it can support Ukrainian energy infrastructure, according to a letter seen by Reuters.
Moscow has been hitting Ukraine's energy infrastructure roughly weekly since early October as it has been forced to retreat on some battlefronts.
Zaporizhzhia casualties
In the Zaporizhzhia region, at least two people were killed and several houses destroyed, the deputy head of the presidential office, Kyrylo Tymoshenko, said.
A Reuters video showed two bodies covered with blankets lying next to a damaged car in the village of Novosofiivka, some 25km (16 miles) east of the southern city of Zaporizhzhia.
"Both of my neighbours were killed," Olha Troshyna 62, said. "They were standing by the car. They were seeing off their son and daughter-in-law."
Missiles also hit energy plants in the regions of Kyiv and Vinnytsia in central Ukraine, Odesa in the south and Sumy in the north, officials said.
About half of the Kyiv region - which does not include the capital and which had a population of about 1.8 million before the war - will be without electricity in the coming days, the region's governor said.
Ukraine had only just returned to scheduled power outages from Monday rather than the emergency blackouts it has suffered since widespread Russian strikes on November 23, the worst of the attacks on energy infrastructure.
But Ukraine's largest private energy provider, DTEK, reported having to disconnect one of its facilities from the power grid, limiting power and heat supply, in what it said was the 17th Russian attack on its sites in the last two months.
The attacks caused damage to main transmission lines and it would take a day or two to restore normal generation in the system, the head of Ukrenergo, the company overseeing the Ukrainian power grid, Volodymyr Kudrytskyi, said.
Ukraine's air force said it downed over 60 of more than 70 missiles fired by Russia on Monday.
Russia has said the barrages are designed to degrade Ukraine's military. Ukraine said they were clearly aimed at civilians and argued it constituted a war crime. Moscow denies that.
Russia says it is waging a "special military operation" in Ukraine to rid it of neo-Nazi nationalists and protect Russian-speaking communities. It wants Ukraine to agree to never join NATO, which Russia sees as a threat to its borders. Ukraine and its allies accuse Moscow of an unprovoked war to grab territory from its pro-Western neighbour.
Reports drones attack two bases deep inside Russia
Russia's defence ministry today said Ukrainian drones attacked two air bases at Ryazan and Saratov in south-central Russia, killing three servicemen and wounding four, with two aircraft damaged by pieces of the drones when they were shot down.
Ukraine did not directly claim responsibility for the attacks. If it was behind them, they would be the deepest strikes inside the Russian heartland since Moscow invaded Ukraine on February 24.
The New York Times, citing a senior Ukrainian official, said drones targeting two military bases were launched from Ukrainian territory, and at least one of the strikes was made with the help of special forces close to the base.
Russia's defence ministry said: "The Kyiv regime, in order to disable Russian long-range aircraft, made attempts to strike with Soviet-made unmanned jet aerial vehicles at the military airfields Dyagilevo, in the Ryazan region, and Engels, in the Saratov region."
It said the drones, flying at low altitude, were intercepted by air defences and shot down. The deaths were reported on the Ryazan base, 185km (115 miles) southeast of Moscow.
Israeli satellite imaging company ImageSat International shared images it said showed burn marks and objects near a Tu-22M aircraft at the Dyagilevo airbase.
The Russian defence ministry called the drone strikes a terrorist act aimed at disrupting its long-range aviation.
It said Russia responded with a "massive strike on the military control system and related objects of the defences complex, communication centres, energy and military units of Ukraine with high-precision air and sea-based weapons" in which it said all 17 designated targets were hit.
Kyiv's forces have demonstrated an increasing ability to hit strategic Russian targets far beyond the 1100 km-long frontline in southern and eastern Ukraine.
Saratov is at least 600km from the nearest Ukrainian territory. Russian commentators said on social media that if Ukraine could strike that far inside Russia, it might also be capable of hitting Moscow.
Previous mysterious blasts damaged arms stores and fuel depots in regions near Ukraine and knocked out at least seven warplanes in Crimea, the Black Sea peninsula annexed by Russia from Ukraine in 2014.
Ukraine has not claimed responsibility for any of the blasts, saying only that they were "karma" for Russia's invasion.
"If something is launched into other countries' air space, sooner or later unknown flying objects will return to (their) departure point," Ukrainian presidential adviser Mykhailo Podolyak tweeted.
-Reuters