Ukraine's General Staff said its forces hit the Syzran oil refinery in Russia's Samara region overnight, triggering explosions and a fire. It said the extent of the damage was still being assessed. The refinery has a processing capacity of around 8.5 million metric tons of crude oil a year and produces gasoline, diesel and aviation fuel used, among other things, to supply the Russian military, the General Staff said. Kyiv also said it struck 10 Russian tankers and four ferries operating in the Sea of Azov, bordered by Russia and Ukraine. It said the tankers were part of Russia's so-called "shadow fleet" used to export oil and petroleum products while circumventing international sanctions, while the ferries supported Russian military logistics. The General Staff also said Ukrainian forces hit a Russian train carrying fuel near the Russian-occupied town of Tokmak in Ukraine's southeastern Zaporizhzhia region on Friday. It added that an assessment of a previous strike on July 10 confirmed damage to an oil-processing unit at the Novatek Ust-Luga processing complex in Russia's Leningrad region. Separately, the commander of Ukraine's Unmanned Systems Forces, Major Robert "Madiar" Brovdi, said the unit had struck 90 Russian vessels over the past week. Russia has increasingly relied on a "shadow fleet" of aging tankers to keep its oil exports flowing despite Western sanctions imposed after its full-scale invasion of Ukraine in 2022. Estimates of the fleet's size vary, with analysts putting it at between about 600 and 1,600 vessels worldwide.