By early afternoon in Europe, benchmark oil was down $1.71 to $94.42 a barrel in electronic trading on the New York Mercantile Exchange. The contract fell 95 cents to settle at $96.13 in New York on Friday.
In London, Brent crude was down $1.61 at $110.65 per barrel on the ICE Futures exchange.
Traders brushed off China's announcement Saturday that it plans to cut its bank reserve requirement by 0.5 percentage points. The move, the third reserve ratio cut since November, is designed to boost lending and spark economic growth.
Investors are worried instead by signs that the country's economy is slowing. The government said Friday that industrial production growth in April weakened and electricity output was little changed.
Also hurting market sentiment was political turmoil in Greece, where parties have been unable to form a government after elections earlier this month.
Speculation that Greece will abandon the eurozone helped boost the U.S. dollar, helping to push down crude prices by making commodities like oil more expensive for investors trading in other currencies. The euro was down to $1.2866 from $1.2925 late Friday in New York.
"The euro/dollar (exchange rate) is starting the week under pressure and the global markets should continue to suffer from some risk-off positioning until we can have a better idea of what happens next in Greece," said analyst Olivier Jakob of Petromatrix in Switzerland.
Some analysts say the recent oil price slump — crude is down more than 10 percent from earlier this month — isn't being driven by global supply and demand fundamentals, but rather seasonal factors which see traders sell assets at the beginning of the summer months.
"There's little to the latest price action than the increasingly self-fulfilling prophecy of `sell it in May and go away', with broader macroeconomic concerns used as a lightening rod," Barclays said in a report. "U.S. oil demand is improving while Asian demand remains robust."
In other energy trading, heating oil was down 3.46 cents to $2.9290 per gallon and gasoline futures lost 2.87 cents to $2.9721 per gallon. Natural gas fell 0.8 cent to $2.501 per 1,000 cubic feet.—