The rise in COVID-19 cases in the world has also exacerbated concerns about the slowdown in the recovery in fuel demand.
And Brent crude futures for December delivery recorded $ 42.70 a barrel, down 1.1%, by 07:30 GMT.
US West Texas Intermediate crude for delivery in the same month fell by 1% to $ 41.27. The two benchmarks rose in the previous session.
“The increase in US stockpiles, along with the recent rise in COVID-19 cases around the world, has prompted investors to adjust positions,” market expert Chiyuki Chen said.
Data from the American Petroleum Institute showed that crude oil inventories in the United States increased by 584 thousand barrels in the week ending October 16, to reach 490.6 million barrels, while analysts expected a decrease of 1 million barrels.