Global oil prices fell Wednesday following a surprising increase in U.S. crude inventories.

U.S. oil benchmark West Texas Intermediate for November delivery shed 47 cents on the New York Mercantile Exchange to $102.66 a barrel, dropping for a fifth day in a row.

European benchmark Brent oil for November delivery fell 32 cents to $108.32 a barrel.

The U.S. Energy Information Administration (EIA) said Wednesday that American crude reserves soared by 2.6 million barrels in the week ending September 20.

Market analysts on average had expected a drop of 900,000 barrels.

"The EIA's inventories ... showed stockpiles increased by a good 2.6 million barrels last week, easily disappointing expectations," said analyst Fawad Razaqzada at trading firm GFT.

John Kilduff of Again Capital expressed surprise at the decline in refinery utilization last week.

Refineries were taking in less oil, running at 90.3 percent of capacity, down from 92.5 percent the prior week, likely due to greater-than-expected refinery maintenance.

The decline in oil also comes amid fresh signs of a possible warming of relations between Iran and the West, which conceivably could lead to an easing of sanctions and allow Iran to export more oil more freely.

However, such a change would not happen overnight, analysts said.