Earlier in month, Kyiv struck eight tankers from Russia's 'shadow fleet' overnight as they were delivering fuel to Crimea.Ukraine's Security Service (SBU) said on Thursday that, in a joint operation with the country's navy, it had struck two Russian "shadow fleet" tankers in the Black Sea using naval drones, reported news agency Reuters.According to the SBU, the vessels Louise 1 and Banda, both under Ukrainian sanctions, were being used to transport Russian crude oil.The shadow fleet refers to ageing tankers that often operate under opaque ownership and changing flags to transport Russian oil while bypassing Western sanctions.Earlier in month, Kyiv struck eight tankers from Russia's 'shadow fleet' overnight as they were delivering fuel to Crimea.In a statement posted on Telegram, Ukraine's drone forces said the vessels were targeted in the Sea of Azov. The drone forces said the tankers were 'delivering fuel to Crimea' and that each vessel, already under international sanctions, had a deadweight of around 7,000 tonnes.Ukraine has stepped up attacks on logistics and energy infrastructure in Crimea in recent weeks. According to Reuters, the campaign has contributed to fuel shortages and prompted authorities to declare a state of emergency in parts of the peninsula, which Russia annexed in 2014, eight years before launching its full-scale invasion of Ukraine in 2022.Kyiv has repeatedly urged its Western allies to tighten enforcement against Russia's so-called "shadow fleet", vessels accused of helping Moscow circumvent international sanctions by transporting Russian oil to global markets.Ukraine has also used naval drones to target tankers transporting Russian oil in the Black Sea as part of a broader effort to disrupt Moscow's energy revenues and military supply chains.