Ukraine attacked multiple regions of Russia on Sunday, killing at least eight people, Russian officials said.
Some of the strikes hit hundreds of kilometres from the front line, according to authorities.
Both Moscow and Kyiv have upped attacks on each other in recent months, as US-led talks aimed at ending the conflict remain largely frozen.
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Kyiv, which denies targeting civilians, says the strikes are fair retaliation for deadly Russian bombardment of its own territory and are aimed at pressuring Moscow into negotiations.
Ukrainian shelling of Russia's Belgorod region bordering Ukraine left three dead, while a separate drone attack on the Saratov region bordering Kazakhstan killed two others, regional authorities said.
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Three were killed in a drone strike on a car in Russia's Udmurtia region, more than 1,000 kilometres (600 miles) from the front line, the region's acting governor Olga Abramova said on Telegram.
"This act is monstrous in its senselessness. These people were definitely not a military target," she said.
Russian air defence systems intercepted 635 Ukrainian drones overnight, the Russian defence ministry said.
