As of 0835 Moscow time, Brent futures had slid by $1.54, to $60.15 a barrel, while WTI futures had dropped by $1.28, to $55.84.

"U.S. crude stocks rose by 7.3 million barrels last week, while the forecast was for a reduction by 2.3 million barrels," the Energy Information Administration reported on Wednesday.

"The market is overflowing with oil before Christmas, as refiners and oil companies usually tend to reduce their reserves to reduce taxes," according to senior energy analyst at the Price Futures Group Phil Flynn.