Brent crude prices climbed in early trading following reports that Ukrainian drones struck an oil refinery in Russia's Ulyanovsk region overnight.
The attack, confirmed by regional governor Alexei Russkih, represents a further deepening of the conflict's reach into Russia's domestic energy production hubs.
The incident adds to a growing list of strikes on Russian processing facilities.
In recent weeks, Ukrainian forces have targeted the Ufa oil refinery for a second time within a week, while debris from unmanned aerial vehicles also ignited a fire at the Ilsky oil refinery in the Krasnodar region.
These coordinated efforts highlight the expanding scope of Ukraine's campaign to disrupt Russian fuel supplies.
Traders are monitoring the situation for signs of immediate output losses.