Russian President Vladimir Putin has threatened Kyiv with retaliation following Saturday's drone attack on the Russian city of Kazan on the Volga, reported German news agency (dpa).
"Whoever tries to destroy something here will be faced with a multiple of the destruction on their territory and will come to regret what they have attempted in our country," the Kremlin chief said during a televised video conference.
On Saturday morning, six Ukrainian drones hit residential buildings in Kazan and a seventh struck an industrial facility. No injuries from the attack were officially reported, while media reports indicated that three people suffered cuts from shattered window glass.
Kazan is located more than 1,000 kilometres from the Ukrainian border. Although Ukraine has not claimed responsibility for the attack, it is considered a response to a Russian missile strike against Kyiv.