Traders say for the time being the price cap imposed on products that trade at a premium to crude, principally diesel - which stands at $100 per barrel - still leaves room for a profit. Russian diesel currently trades at around $75 per barrel. They also note vessel availability is higher for fuel than for crude.

Ukrainian drones hit a Russian oil refinery in the city of Ryazan overnight, causing a fire and damaging equipment at one of Russia's biggest refineries, four industry sources told Reuters on Friday.

The reported strike comes two nights after Ukrainian forces launched a joint attack against the refinery that allegedly damaged multiple on-site facilities.