A worker stands next to a pump jack at an oil field Sergeyevskoye owned by Bashneft company north from Ufa, Bashkortostan, Russia.

Oil prices tumbled more than 4% on Wednesday to a seven-month low, extending recent heavy losses following a surprise build in U.S. crude stockpiles and fears that demand will shrink due to Washington's escalating trade war with Beijing.

Brent crude futures were down 4.4%, at $56.35 a barrel, setting a seven-month low. Prices have lost more than 20% since their 2019 peak in April. U.S. West Texas Intermediate (WTI) crude futures settled down 4.7%, at $51.09 a barrel.