Oil prices slid Thursday after weak Chinese manufacturing data raised fears about global economic growth and traders awaited key US jobs data.
New York's main contract, light sweet crude for delivery in January, ended at $100.20 a barrel, down 16 cents from Wednesday's closing level.
The futures contract clawed back from steeper losses in late-session trading to finish above $100.
In London, Brent North Sea crude for January sank $1.53 to settle at $108.99.
Europe's debt crisis continued to overhang markets as eurozone leaders struggle to contain the contagion sweeping the region's financial system.
"Again we're seeing further trepidation in the market here in terms of what's going on in Europe," said Matt Smith, an analyst at Summit Energy.
Markets were under pressure after official data showed China's manufacturing activity shrank for the first time in nearly three years.
The purchasing managers index fell to 49 in November, down 1.4 points from October, marking the first contraction since February 2009, the China Federation of Logistics and Purchasing said.
IHS Global Insight analyst Alistair Thornton said the "shocking" data showed the world's second-largest economy, the engine of the global economy, was "sagging under the weight of this year's credit tightening."
Addison Armstrong at Tradition Energy noted the data's negative impact on market sentiment, saying China is "the largest user of energy and base metals."
In the United States, a weekly report on new unemployment claims showed a slight rise for the second straight week ahead of Friday's November labor data.
"The broader picture now suggests that, having reversed the sharp rise during August, claims are now trending broadly sideways," Peter Newland at Barclays Capital said.
On Friday, economists expect the Labor Department will report the unemployment rate was unchanged at 9.0 percent for the second month running.
Since May 2009 the jobless rate has been stuck at 8.8 percent or higher as the world's largest economy, and biggest oil consumer, recovers slowly from recession.