KEEPING SCORE: The Standard & Poor's 500 index fell 19 points, or 1.1 percent, to 1,839 as of 12:24 p.m. (1724 GMT). The index is on track for its biggest drop in a month. The Dow Jones industrial average fell 217 points, or 1.3 percent, to 16,106. The Nasdaq composite dropped 60 points, or 1.4 percent, to 4,247.
WORLD MARKETS: Markets also fell in Europe. Germany's DAX sank 3.4 percent, to 9,358. Britain's FTSE 100 dropped 1.5 percent, to 6,708 and Russia's benchmark stock index plunged 12 percent, to 1,115.
SAFETY FIRST: Gold and bond prices rose as investors put money into safer assets. The price of gold gained $31.20, or 2.4 percent, to $1,352.60 an ounce. The yield on the 10-year Treasury note fell to 2.61 percent from 2.65 percent late Friday.
THE REACTION: Stock markets are reacting exactly as one would expect them to in a time of heightened global political tensions, said Phil Orlando, chief equity market strategist at Federated investors. Investors are selling riskier assets like stocks and buying safer securities like U.S. Treasurys and gold.
"We just have no way of knowing how this is going to play out,'' Orlando said. "It's a very uncertain situation and the market is demonstrating its unhappiness with that.''
RUSSIAN STOCKS: Shares of Russian companies traded in the U.S. also plummeted. Mechel, a mining company, fell 15 cents, or 8.4 percent, to $1.74; Phone company VimpelCom fell 78 cents, or 7.7 percent, to $9.37. Oil company LukOil fell $4.05, or 7.4 percent, to $50.35.
ENERGY PRICES: The price of crude oil climbed $2.12, or 2.12 percent, to $104.64 a barrel following warnings by Washington and other governments that Russia, a major oil exporter, might face sanctions after it seized control of Ukraine's Crimean Peninsula. Russia was the world's second-largest producer of oil in 2012, accounting for 12.6 percent of global supplies, according to the International Energy Agency.
ON THE HOME FRONT: The tensions in the Ukraine outweighed positive reports on the U.S. economy. U.S. manufacturing expanded at a faster pace in February as new orders and stockpiling rose.
Americans spent more in January, but the increase came from a surge in spending on heating bills during the harsh winter. Spending in areas such as autos and clothing declined. Spending rose 0.4 percent in January after a 0.1 percent gain in December, the Commerce Department said Monday. The December figure was revised down from a 0.4 percent increase.
IT'S COLD OUTSIDE: Darden Restaurants, the parent company of Olive Garden, slumped $2.61, or 5.1 percent, to $48.44 after the restaurant operator said that exceptionally rough winter weather reduced earnings in its latest quarter by about 7 cents per share. Expenses related to the company's plan to split off its Red Lobster chain also hurt earnings.