By early afternoon in Europe, benchmark oil for May delivery was down 59 cents to $102.43 a barrel in electronic trading on the New York Mercantile Exchange. The contract rose 24 cents to settle at $103.02 per barrel in New York on Friday.
In London, Brent crude for May delivery was down 45 cents at $122.43 per barrel on the ICE Futures exchange.
The unemployment rate in the 17 countries using the euro rose to 10.8 percent in February, its highest level since the currency was introduced in 1999, stoking fears that the bloc is back in recession.
Also putting pressure on oil prices, a survey of the European manufacturing sector indicated a fall in activity.
On the other hand, China said Sunday that its manufacturing activities gained momentum for a fourth straight month in March. The data contradicted a report by HSBC last month that suggest China's industrial production was slowing.
Increased consumption from developing countries has accounted for the majority of global crude demand growth in recent years. China is the world's second-largest oil consumer and the surge in its demand over the last decade or so has fueled a crude price jump from $10 in 1998.
"Almost the entirety of global oil demand growth will come from Brazil, India, China and Saudi Arabia," Barclays Capital said in a report. "Demand outside those countries has not been growing at all, and we expect that pattern to continue into 2012."
Investors are also watching tensions over Iran's nuclear program. President Barack Obama said Friday he plans to go ahead with economic sanctions against countries buying oil from Iran, while China rejected the decision, saying that Washington had no right to unilaterally punish other nations.
In other energy trading, heating oil was up 0.5 cent at $3.1706 per gallon and gasoline futures rose 0.45 cent at $3.3126 per gallon. Natural gas slid 0.2 cent at $2.124 per 1,000 cubic feet.—
Alex Kennedy in Singapore contributed to this report.