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.Ukrainian President Volodymyr Zelensky called on Kyiv's Western partners to supply more air defense systems to protect his country's skies, as the air force said it shot down 21 of 34 incoming missiles.Moscow has launched some of its biggest 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 said it hit two oil refineries and a military air base in southern Russia its own wave of overnight drone attacks."Thirty-four Russian missiles overnight.

We managed to shoot down some of them.

But the world has every opportunity to help (us) shoot down every missile and every drone," Zelensky said in a post on Telegram.Energy facilities were hit in at least three regions -- including Lviv and Ivano-Frankivsk in the west, hundreds of kilometers from the front line -- Energy Minister German Galushchenko said in a Facebook post.One of the missiles landed 15 kilometers (nine miles) from the Polish-Ukrainian border, Poland's Prime Minister Donald Tusk said.Kyiv says Moscow is escalating 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.Energy rationingThe 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 urged people and businesses to limit their power usage."We ask all consumers to consume electricity sparingly.

Industry is asked to maximize 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 in peak evening hours.At least two people were killed in separate shelling attacks on the northeastern Kharkiv region and southern Kherson region, Ukrainian officials said.The spate of missile and artillery attacks also injured more than a dozen.Russia's defense ministry said Saturday that over the last week it had carried out 35 "group strikes" against Ukrainian energy sites, military factories, railway facilities, air defense systems and other targets.The United States on Friday announced a $6 billion package of military supplies to Kyiv to include key air defense munitions and artillery rounds.68 drones downedUkraine launched its own massive drone attack on Russia's southern Krasnodar region overnight.A Ukrainian defense source told AFP it 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 said Ukraine had launched one of its largest-ever attempted drone attacks on the Krasnodar region."Air defenses destroyed and intercepted 66 Ukrainian drones over the territory of the Krasnodar region and two over the Crimean peninsula," the defense ministry said.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 a few kilometers from the border.Kyiv has hit several oil refineries in western Russia 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.