In afternoon trade, European benchmark Brent North Sea crude for January delivery hit USD 41.05 per barrel - a level last seen on February 24, 2009.
US benchmark West Texas Intermediate for January struck USD 37.88 - which was last witnessed in August earlier this year.
The Organization of the Petroleum Exporting Countries - which pumps about 40 per cent of the world's crude oil - decided on Friday against cutting output to raise prices.
"The decision by OPEC members to keep oil production output at record high levels has seen oil prices plummet again," said Sanjiv Shah, chief investment officer of Sun Global Investments.
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He added that the decision "suggested that the organisation was effectively abandoning its long-term strategy of limiting production and acting as a cartel, leading to more downward pressures on oil prices in the short term".
OPEC countries are currently producing an estimated 32 million barrels per day, above the group's agreed 30 million barrel target.
But it has now put off a production reassessment to its next meeting on June 2, 2016, and gave no official output figures following Friday's latest meet.
In late afternoon deals on today, Brent stood at USD 41.16, down USD 1.84 from Friday's closing level.
WTI was USD 1.88 lower at USD 38.09.
"Crude oil prices were no doubt compressed by the lack of an agreement at the OPEC, signalling that the supply glut will persist longer," said analyst Bernard Aw at IG Markets in Singapore.
EY analyst Sanjeev Gupta added that market attention had now turned to an upcoming meeting of Fed policymakers and to the latest economic data from China, the world's top energy consumer.
Markets are watching whether the Fed will raise interest rates on December 16, a move that will boost the dollar.
A stronger US currency makes dollar-priced oil more expensive to holders of weaker currencies, and therefore tends to dent demand and weigh on prices.