US benchmark West Texas Intermediate for delivery in February briefly dropped to $49.95 a barrel, but then rose to $50.20 a barrel. The February contract for Brent crude also touched a new five-and-a-half-year low, dropping to $53.08 per barrel.

MOSCOW, January 5 (Sputnik) — US crude oil prices fell below $50 a barrel Monday for the first time since April 29, 2009 amid worries about a surplus of global supplies and weakening demand on oil markets.

Near 16:30 GMT, US benchmark West Texas Intermediate for delivery in February dropped to $49.95 a barrel, but then rose to $50.20 a barrel.

The February contract for Brent crude also touched a new five-and-a-half-year low, dropping to $53.08 per barrel.

The breach of the $50 mark came on a rocky day in global financial markets, with the Dow ending down more than 200 points and European stocks losing more than two percent.

Now, the two crude oil benchmarks have lost more than half of their value since June 2014 on worries about lackluster demand and a decision by the Organization of the Petroleum Exporting countries (OPEC) not to cut output in response to lower prices.

"People are thinking about promises from OPEC, mostly Saudi Arabia, that they’ll continue to produce at very high levels," Bart Melek, head of commodity strategy at TD Securities, told AFP. "On the demand side of the equation, what we’re getting is basically a lack of demand growth… as Europe is potentially in crisis."

A weak euro may also have driven oil prices to new low as it reduces the purchasing power of euro holders for dollar-denominated oil.

Earlier on Monday, the euro hit a nine-year low against the US dollar on the Greek turmoil and speculation the European Central Bank is preparing for large-scale bond purchases.