Russia fired 69 missiles at energy facilities and Ukrainian forces shot down 54, Ukrainian military chief Gen. Valerii Zaluzhnyi said.
After more than 10 months of fighting, Russia and Ukraine are locked in a grinding battle of attrition.
The Ukrainian military has reclaimed swaths of Russian-occupied territory in the country's northeast and south, and continues to resist persistent Russia attempts to seize all of the industrial Donbas region in the east.
At the same time, Moscow has targeted Ukrainian power facilities and other key infrastructure in a bid to weaken the country's resolve and force it to negotiate on Russian terms.
The time between strikes has increased in recent weeks, though, leading some commentators to theorise Russia is trying to ration its missile supply.
The Ukrainian military has reported success in shooting down incoming Russian missiles and explosive drones in earlier attacks but many cities have gone without heat, internet and electricity for hours or days at a time.
Ukrainian Prime Minister Denys Shmyhal said a number of energy facilities were damaged during what he said was the 10th such large-scale attack on his country.
“Russia is trying to deprive Ukrainians of light before the New Year,” Shmyhal wrote in a Telegram post.
He said that emergency blackouts may be necessary “in some areas.”
About 90% of Lviv was without electricity, Mayor Andriy Sadovyi wrote on Telegram. Trams and trolley buses were not working, and residents might experience water interruptions, he said.
Meanwhile, a Telegram channel affiliated with the presidential press service of Belarus said a Ukrainian S-300 air defense missile landed in Belarusian territory of Belarus early Thursday.
It said the missile could have veered off course accidentally and there were no casualties.
The Belarusian Defense Ministry said later that the missile was downed by the Belarusian air defence over the western Brest region and fell into a field, according to a statement carried by the state Belta news agency
Belarus served as a staging ground for Russia's Feb. 24 invasion of Ukraine.
The governor of Russia's Saratov region, Roman Busargin, said Russian air defences downed an “unidentified object” near the city of Engels, home to a Russian air base that serves as the main hub for nuclear-capable strategic bombers that are engaged in launching missile strikes on Ukraine.
The Russian military said the Engels base was targeted by Ukrainian drones twice this month, most recently on Monday.
Russia's Defence Ministry said three servicemen were killed by fragments of a downed Ukrainian drone.
Ukrainian authorities have maintained ambiguity about attacks on Russian soil, stopping short of claiming responsibility for them.
Earlier this month, the United States agreed to give a Patriot missile battery to Ukraine to boost the country's defense.
The U.S. and other allies also pledged to provide energy-related equipment to help Ukraine withstand the attacks on its infrastructure.
Mykhailo Podolyak, an adviser to Ukrainian President Volodymyr Zelenskyy, said Russia was aiming to “destroy critical infrastructure and kill civilians en masse.”
Kuleba, the Ukrainian foreign minister, said Monday that his nation wants a “peace” summit within two months at the United Nations with Secretary-General António Guterres as mediator.
He said Russia must face a war-crimes tribunal before his country directly talks with Moscow but that other nations should feel free to engage with the Russians.
Commenting on the summit proposal Thursday, Russian Foreign Ministry spokeswoman Maria Zakharova dismissed it as “delirious” and “hollow,” describing the proposal as a “publicity stunt by Washington that tries to cast the Kyiv regime as a peacemaker.”
Russian officials have said that any peace plan can only proceed from Kyiv's recognition of Russia's sovereignty over the regions it illegally annexed from Ukraine in September.