The cartel rejected a move by Iran to cut production quotas to raise prices, although it appeared that the big driver in the decline of oil prices was anxiety about Europe.

The euro slid below $1.30 and Italy's bond auction forced it to pay even higher rates to entice lenders — 6.47 percent, up from 6.3 percent a month ago. The higher rates were seen as a sign that last week's agreement to tighten the rules against overspending by eurozone governments has failed to restore investor confidence.

Oil prices fell $5.19, or 5.2 percent, to end at $94.95 per barrel.

Chevron Corp. shares fell $3.12, or 3 percent, to $100.50 in afternoon trading. Occidental Petroleum Corp. was down $3.25, or 3.5 percent, to $88.43. Shares of Marathon Oil Corp. dropped 69 cents, or 2.5 percent, to $26.95, and Exxon Mobil Corp. shares fell $1.09 to $79.44.

Shares of oil service firms fell, too. Schlumberger NV was down $3.46, or 4.9 percent, to $66.95. Halliburton Co. fell 96 cents, or 3 percent, to $30.90, while National Oilwell Varco Inc. was down $3.09, or 4.5 percent, at $65.86. Helmerich & Payne Inc. fell $3.17, or 5.5 percent, to $54.15.