New York's main contract, light sweet crude for December delivery, shed 34 cents to 80.06 dollars a barrel.

Brent North Sea crude for December delivery slipped 53 cents to 78.36 dollars.

Prices eased after breaking through the 80-dollar mark in New York on Wednesday, reflecting concerns over weak demand, analysts said.

"The fundamentals of the markets are still weak... and there are no signs of steadily growing demand," said Jason Feer, Asia-Pacific vice-president of energy market analysts Argus Media in Singapore.

He added that data released by the US Department of Energy (DoE) on Wednesday showing an unexpected dip in US crude reserves was "overall not that much" in the larger scheme of prices.

The DoE announced that crude reserves in the world's largest energy consumer sank by four million barrels in the week ending October 30, surprising analysts, who were expecting a rise.

Oil prices have climbed as commodities gained a boost from gold futures, which have struck a series of record highs.