New York's main contract West Texas Intermediate (WTI) for delivery in December sank to USD 93.41 per barrel -- which was the lowest level since June 24. It later stood at USD 93.66, down 96 cents from yesterday's close.
Brent North Sea crude for December dipped 35 cents to USD 105.88 a barrel in late afternoon trade.
Analyst Fawad Razaqzada, at trading firm GFT, said that the market was hit by "ongoing concerns over rising US crude inventories and (the) weaker global demand outlook".
In addition, a better-than-expected reading on the US services industry pushed the dollar higher, in turn weighing on oil prices.
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A rising greenback makes dollar-denominated oil more expensive for buyers using cheaper currencies.
Later today, meanwhile, industry body the American Petroleum Institute will publish its weekly oil inventory data.
And tomorrow, the US government's Energy Information Administration will issue its official snapshot of crude reserves for the week ending November 1.
Crude inventories in the United States have climbed for the past six weeks, to about 28 million barrels, raising concerns about oversupply in the world's largest economy and top crude consumer.
Libyan oil production levels also remain in focus, analysts said.