At least 13 people were killed, including a child, and 39 injured in a Ukrainian drone attack on industrial and civilian targets in the city of Nizhnekamsk, authorities said on Monday, one of the heaviest civilian tolls in Russia in months.
Ukraine's military said it had hit Tatneft's TANECO oil refinery in the Tatarstan region, about 800 km (497 miles) east of Moscow, adding that a fire was recorded at the facility.
Russian investigators said they had opened a criminal case into what they qualified as a terrorist attack, saying in a statement that Ukraine had struck residential areas and that a child was among those civilians killed.
The head of Russia's Tatarstan region, Rustam Minnikhanov, has declared a period of mourning, Radmir Belyayev, the mayor of Nizhnekamsk, said in a statement on Telegram.
In verified videos by Reuters on social media, smoke can be seen rising over the oil refinery.
The TANECO refinery, which was also hit by Ukraine in early June, processed 17 million tons of crude oil in 2024, producing 2.7 million tons of gasoline and 8.5 million tons of diesel fuel.
Ukraine has stepped up its strikes on Russian oil refineries in recent months in a campaign that has caused fuel shortages in many parts of Russia, although authorities say that most of those initial problems have since been resolved.
Ukraine says it wants to bring the price of Russia's war home to ordinary Russians. Moscow has imported fuel from overseas to help bolster supplies.
On Sunday, both sides accused each other of lethal attacks. Three people were killed and 37 wounded in a Russian attack on the eastern Ukrainian city of Kharkiv, where a multi-storey apartment block was hit, while authorities in Russia's Belgorod said five were killed and 25 wounded by a Ukrainian drone attack.
Ukraine and Russia have repeatedly said they do not target civilians.
