Russia's energy ministry declined to comment.

Oil output in the first three days of June was the lowest since mid-2016, according to Reuters calculations.

Russian oil output in May fell to 11.11 million bpd, its lowest level since June 2018, from 11.23 million bpd in April.

The production fall resulted mainly from the closure due to oil contamination of Russia's Druzhba pipeline, which usually ships 1 million bpd, or 1 percent of global oil demand.