Overnight Ukrainian drone strikes targeted major energy and petrochemical facilities in central Russia’s Samara region and the republic of Tatarstan, monitoring groups reported Friday.

Mayor Radmir Belyayev of Tatarstan’s industrial city of Nizhnekamsk said four people were hospitalized after a Ukrainian drone struck a multistory residential building. The exiled outlet Astra shared eyewitness video of the detonation and the subsequent fire.

Ukrainian monitoring channels reported that two of the targets included Nizhnekamskneftekhim, Russia’s largest producer of synthetic rubber and plastics, and the Taneco oil refinery.

Tatarstan Head Rustam Minnikhanov, without identifying the plants by name, said that “the attacked enterprises were swiftly addressing the aftermath.” Mayor Belyayev said all public events were canceled on Friday, which marks the Russia Day holiday, due to the drone threat.

In the neighboring Samara region, the mayor of another industrial city, Tolyatti, said Ukrainian drone attacks damaged an “industrial facility.” Ukrainian monitoring groups identified the target as synthetic rubber and chemical component producer Tolyattikauchuk.