A massive Ukrainian drone attack on the city of Nizhnekamsk in Russia's Tatarstan has killed at least 12 people, 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 39 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.
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.