The West Texas Intermediate for August delivery shed 1.28 U.S. dollars to settle at 39.62 U.S. dollars a barrel on the New York Mercantile Exchange, while Brent crude for September delivery lost 94 cents to close at 42.35 dollars a barrel on the London ICE Futures Exchange.
"The increasing number of new Covid-19 cases in the U.S. and worldwide is sparking concerns about demand trends," Eugen Weinberg, analyst at Commerzbank Research, said in a note on Thursday.
"In view of the uncertainty and considerable fluctuations on both the supply and demand side, prices could be expected to show significantly greater volatility," Weinberg added.
The prices were also pressured as data showed U.S. crude oil inventories increased last week.
U.S. commercial crude oil inventories, excluding those in the Strategic Petroleum Reserve, increased by 5.7 million barrels during the week ending July 3 from the previous week, the U.S. Energy Information Administration reported Wednesday.