The assault, a day after Vladimir V. Putin was sworn in for a fifth term as Russian president, is part of a wider campaign to cut off power to Ukraine’s civilians.

Russia’s oil storage capacity is limited. When a refinery is destroyed or damaged, therefore, extracted crude oil cannot simply be stocked for later use. This leaves Russian producers with just two options: increasing exports of crude oil or shutting wells and reducing production.

Russia on Thursday marks the Soviet Union's victory over Nazi Germany in World War Two as relations with the West spiral deeper into crisis over the advance of Russian troops against Ukraine's Western-backed forces.

Ukraine on Wednesday said it was limiting power supplies across the country and warned of possible blackouts after a "massive" wave of Russian missiles and drones targeted the country's battered