Crude oil tumbled sharply on Tuesday, amid indications Saudi Arabia lowered prices to buyers in the U.S.
On the New York Mercantile Exchange, crude oil for delivery in December fell to a session low of $77.22 a barrel, a level not seen since October 2011.
Prices recovered to last trade at $77.51 a barrel during European morning hours, down $1.27, or 1.61%.
Elsewhere, on the ICE Futures Exchange in London, Brent for December delivery lost $1.33, or 1.57%, to hit $83.45 a barrel.
Saudi Arabia on Monday cut its selling price for oil to the U.S., suggesting that the kingdom is trying to compete with U.S. shale oil.
London-traded Brent prices have fallen nearly 27% since June, when it climbed near $116, while WTI futures are down almost 28% from a recent peak of $107.50 in June.
Concerns over weakening global demand combined with indications that the Organization of the Petroleum Exporting Countries will not cut output to support oil markets have weighed on prices in recent weeks.
Some market analysts believe that only a cut in production by the oil cartel will halt the decline in prices.
Oil ministers from the 12-member group are scheduled to meet in Vienna on November 27 to consider whether to adjust their production target for early 2015.