Russia launched a "massive" missile strike at Ukraine overnight, damaging four power plants in the latest barrage targeting the country's energy supply, officials in Kyiv said on Saturday.
Two people were killed and at least 10 more wounded in Russian shelling.
Moscow has launched some of its largest ever strikes on Ukraine's energy facilities in recent months, knocking out a significant chunk of production, and triggering blackouts and energy rationing across the country.
Ukraine also fired more than 60 drones at southern Russia overnight, Moscow said, in one of its largest overnight drone attacks. Kyiv claimed to have hit two oil refineries and a military air base.
"Russian armed forces staged another massive missile attack on Ukraine," the Ukrainian army said in its regular morning update.
"The enemy has once again attacked the country's energy infrastructure. In particular, facilities in Dnipropetrovsk, Ivano-Frankivsk, and Lviv regions were attacked. There is damage to equipment," Energy Minister German Galushchenko said in a Facebook post.
The Lviv and Ivano-Frankivsk regions are in Ukraine's west, bordering the EU and hundreds of kilometres from the frontlines.
Ukraine's air force said Moscow had fired 34 missiles, of which 21 were shot down.
Kyiv says Moscow is escalating its attacks from the air and on land ahead of nationwide celebrations on May 9, when Russia marks victory in World War II, and while Ukraine awaits the arrival of crucial US weapons.
The DTEK power operator said equipment at four of its thermal power plants was "severely damaged" in the overnight strikes.
State electricity operator Ukrenergo said it had disconnected its main overhead power line in the west of the country as a preventative measure.
Officials asked energy users to limit their power usage.
"We ask all consumers to consume electricity sparingly. Industry is asked to maximise electricity imports and use alternative power sources," Ukrenergo said in a statement.
The head of the western Lviv region called on residents not to use kettles, irons, washing machines and microwaves between 7:00pm and 10:00pm to preserve limited energy supplies.
Separate shelling on a village close to the Russian border in the northeastern Kharkiv region killed one person on Saturday, Ukraine's state emergency services agency said.
One person was also killed and eight wounded in shelling of the southern Kherson region, Ukraine's national police said.
The overnight missile strikes injured two people in the central city of Kryvyi Rih, regional governor Sergiy Lysak said, and wounded one in the northeastern Kharkiv region, emergency services said.
Ukraine also launched its own massive drone attack on Russia's southern Krasnodar region overnight.
A Ukrainian defence source told AFP its drones had hit two oil refineries and a military airfield in the region, just east of the annexed Crimean peninsula.
"Ukrainian drones struck the atmospheric distillation columns of the Ilsky and Slovyansky refineries. These are key technological facilities," the source said.
Russian officials in the Krasnodar region reported a fire at an oil refinery in the town of Slavyansk-on-Kuban.
The refinery partially suspended operations as a result, Russian state media reported, citing a company representative.
Videos and photos on social media showed a large fire raging overnight at the site after a series of blasts.
Moscow earlier said that Ukraine had launched one of its largest ever attempted overnight drone attacks on the Krasnodar region.
"Air defences destroyed and intercepted 66 Ukrainian drones over the territory of the Krasnodar region and two over the Crimean peninsula," the defence ministry said in a statement.
The governor of Russia's Belgorod border region said later on Saturday that five people were injured when a Ukrainian drone fell on a road in a village a few kilometres from the border.
Kyiv has hit several Russian oil refineries in the western part of the country in recent months, despite reports of concern in Washington that the strikes could be seen as escalatory and might drive up global oil prices.
Ukraine says targeting Russia's vital energy sector is legitimate as it is a source of fuel and funds for the Russian army.
