A look at highlights from the day's business news:

Stocks mired in sell-off

Stocks extended losses to end sharply lower Wednesday, amid more signs of a deepening crisis in Europe.       

Moody's said it was considering a downgrade of Portugal's debt, while three people were reported dead due to riots in Greece.

The Dow Jones industrial average lost 60 points, or 0.6 percent, to end at 10,866.83. The blue-chip index had fallen more than 100 points earlier in the trading day.

The S&P 500 index fell 8 points, or 0.7 percent, to close at 1,165.87. The Nasdaq composite was down 22 points, or 0.9 percent, to settle at 2,402.29.

Oil prices tumble

Oil prices plunged Wednesday as a stronger dollar, fueled by widespread fear of Europe's sovereign debt woes, lessened the appeal of buying crude.

But gasoline prices continued their climb, rising 1.5 cents a gallon in the latest survey conducted for motorist group AAA.

What prices are doing: Crude for June delivery fell $2.77, or 3.3 percent, to settle at $79.97 a barrel. This is the first day oil has settled below $80 since March 15.

U.S. bonds gain on Portugal's pain

U.S. debt prices continued to rally Wednesday, after Moody's said it was considering cutting Portugal's credit rating one to two notches.

Bond investors also welcomed the news that the government will issue fewer new U.S. Treasurys than it did last quarter, due to a recovering economy.       

What prices are doing: In morning trading, the benchmark 10-year note rose 13/32 to 100-21/32, pushing the yield down to 3.55 percent. Bond prices and yields move in opposite directions.

The 30-year bond rose 16/32 to 104 with a 4.39 percent yield. The 2-year note rose to 100-8/32 with a 0.88 percent yield. The 5-year note gained 12/32 to 100-31/32, yielding 2.3 percent.

What's moving the market: Moody's Investors Service announced Wednesday that it is considering cutting Portugal's credit rating to reflect its growing deficit.

Dollar rises on European debt fears

The dollar rose Wednesday, trading at fresh one-year highs against the euro, as fears about Europe's debt crisis sent investors away from riskier assets.

What prices are doing: The dollar gained 1.3% versus the euro to $1.2822 after climbing to its highest level since March 2009 in earlier trading. It was up 0.25% on the pound to $1.5106. Against the yen, the dollar fell 0.8% to ¥93.78.

What's moving the market: The dollar remained strong, as persistent debt fears weighed on global stock markets.

European stock markets were down across the board Wednesday, while U.S. stocks closed sharply lower, after plunging the day before. Other risky asset classes, such as oil, were also down as investors sought refuge in quality.

CNNMoney.com reporters Annalyn Censky, Chavon Sutton and Julianne Pepitone contributed to this report.