A massive Ukrainian drone attack on the city of Nizhnekamsk in Russia's Tatarstan has killed at least 13 people, the authorities said on Monday.
The head of the Tatarstan Republic, Rustam Minnikhanov, has declared a period of mourning following the attack. His government, based in the major city of Kazan, said a further 48 people were injured.
The mayor of Nizhnekamsk, Radmir Belyayev, reported a major attack by Ukrainian drones on industrial facilities and civilian targets. Ukrainian media reported that one of the largest oil refineries in the area was targeted.
The General Staff in Kiev later confirmed the attack on the Taneko refinery in Nizhnekamsk.
In its defensive struggle against Moscow's invasion, Kiev is targeting facilities belonging to the Russian oil industry.
The aim is to deprive the Russian war machine of vital revenue, such as that derived from energy exports. Recently, an increasing number of civilians have been killed in Ukrainian counter-attacks.
Ukraine also reported injuries on Monday, with 13 wounded in a Russian airstrike on the south-eastern city of Zaporizhzhya.
The region's military governor, Ivan Fedorov, said a glide bomb was dropped on the industrial city, causing damage to residential buildings and cars.
The city is under almost constant air-raid alarms, with the front line just 20 kilometres away.