Oil prices in New York dropped to an 18-month low Wednesday after the US petroleum inventory report showed mounting stockpiles in the world's top crude consumer.
US benchmark West Texas Intermediate for November delivery fell $1.54 to $87.31 a barrel, the lowest level since April 2013.
European benchmark Brent crude for delivery in November fell 73 cents to $91.38 a barrel.
The Department of Energy said Wednesday that American crude reserves climbed by 5.0 million barrels in the week ending October 3, much above the 1.9 million billion forecast by analysts surveyed by Dow Jones Newswires.
Andy Lipow, head of Houston  consultancy Lipow Oil Associates, said the drop in prices was due to the US inventory report.
The report was "just one more news item in a series of bearish headlines that have been plaguing the oil market over the last couple of weeks," Lipow said.
Lipow said other "bearish" developments include the downgrade in the International Monetary Fund's economic growth forecast and news of higher output from the Organization of Petroleum Exporting Countries.