West Texas Intermediate futures for December delivery fell to $45.86 (-0.93%), while Brent crude fell to $48.43 (-0.57%) after data from the American Petroleum Institute showed a larger-than-expected increase in U.S. crude stocks.

The API reported on Tuesday that U.S. commercial crude stocks rose by 7.1 million barrels to 473 million barrels in the week ending October 16, while analysts had expected a more modest increase of 3.9 million barrels.

The Energy Information Administration is due to release its more precise inventory data later today.

Investors are also waiting for the result of today's meeting of the Organization of the Petroleum Exporting Countries and non-OPEC oil producers.