In morning London deals, Brent North Sea crude for delivery in February dived to a 5.5-year low at USD 49.81 a barrel. New York crude had already slumped under USD 50 on Monday.
"The move below USD 50 shows how momentum is everything here," CMC Markets analyst Michael Hewson told AFP.
"With no sign that OPEC will do anything about over-production, it seems likely that we could well see further declines towards USD 40 in the coming weeks -- particularly given that demand shows no signs of picking up.
Crude futures had tumbled Tuesday to fresh multi-year lows in another stormy day for global financial markets, as OPEC kingpin Saudi Arabia blamed weak global economic growth and said it will stick to its guns on production policy.
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On Monday, Saudi Arabia reportedly cut its European and US export prices in order to maintain market share.
Losses accelerated in November after the 12-nation Organization of the Petroleum Exporting Countries (OPEC) cartel decided not to cut output in response to lower prices and oversupply.
OPEC opted to keep its oil output ceiling at 30 million barrels per day (mbpd) despite ample global supplies.
Analysts said the move was aimed at stifling competition from new market players with higher costs -- in particular US shale oil producers.