Four people were killed in a Ukrainian drone attack on an industrial zone in Volgograd, in Russia’s southern region, regional governor Andrei Bocharov said on Friday. Two other people were injured in the strike, described as the deadliest attack on the city so far. Unverified video posted on social media showed a large fire at a Volgograd oil refinery, which has been targeted several times before. Volgograd is home to a large oil refinery run by Lukoil and other industrial facilities. Residents reported loud explosions overnight, and online footage circulated showing the fire at the refinery. There was no official confirmation that the refinery was hit, and Lukoil did not respond to a request for comment. The attack comes after Ukraine sharply stepped up assaults on Russian oil refineries since the end of October, when an energy ceasefire announced by US President Donald Trump failed to take hold. Industry sources said the refinery attacks have temporarily reduced Russia’s oil refining capacity by about 30% since the campaign increased. Lukoil’s website says the Volgograd refinery has a processing capacity of about 14 million tonnes of crude oil per year, or roughly 280,000 barrels per day, about 5% of Russia’s total refining volume. The latest status of the incident is that the governor reported four deaths and two injuries, with no official confirmation of which industrial site was struck and no further details released.