Editor's note: This is a developing story and is being updated.Ukrainian drones reportedly struck a Russian oil refinery as well as a chemical production plant overnight on May 20, Russian Telegram media channels reported.Smoke was seen billowing out of an oil refinery near the city of Kstovo in Nizhny Novgorod Oblast following a Ukrainian drone attack on the region, independent Russian Telegram media channel ASTRA reported.Ukraine's military also reportedly struck the Nevinnomyssk Azot plant in Russia's southern Stavropol Krai overnight on May 20, Russian Telegram media channels reported.The plant is one of Russia's largest producers of mineral fertilizers and chemicals used in manufacturing explosives. The plant produces up to 1 million tons of ammonia and more than 1 million tons of ammonium nitrate annually, materials used in the production of explosives and artillery shells.Nevinnomyssk Mayor Mikhail Minenkov reported active air defenses above the city amid the attack. Local residents reported explosions and a fire seen in the city earlier in the night, according to Russian Telegram channels.Stavropol Krai Governor Vladimir Vladimirov claimed in a post on Telegram that air defenses had repelled a drone attack aimed at an unspecified "industrial zone" in Nevinnomyssk, with no damage caused.The Kyiv Independent cannot verify the reports nor claims made by Russian officials. The extent of the damage caused was not immediately clear.Although the target of the attack on the oil refinery was not immediately clear, the reported strike on the facility comes just two days Ukrainian forces struck the Lukoil-Nizhegorodnefteorgsintez oil refinery in Kstovo.Following the attack, the General Staff said the refinery "is one of the largest oil refining enterprises of the Russian Federation" with a processing capacity of around 17 million tons of oil annually. According to the Ukrainian military, the facility produces gasoline, diesel fuel, and aviation fuel "used to support the needs of the Russian occupation forces."Nevinnomyssk Azot has also been repeatedly targeted during the full-scale war, most recently in a reported strike on May 16. Previous strikes on the plant have also reported in March and January 2026, as well as multiple times in 2025. The latest alleged attack marks at least the seventh time Ukraine has targeted the facility since the start of Russia's full-scale invasion.Ukraine's military has not yet commented on the attack.Ukraine has increasingly relied on domestically produced drones to strike targets deep inside Russia, particularly facilities tied to oil refining, logistics, and defense production.Kyiv continued its attacks against Russian oil refineries on May 19, striking an oil pumping station in Yaroslavl Oblast.