NEW YORK (AP) — U.S. stocks are opening sharply lower as worries intensify about China's economy and dropping oil prices.

China's main stock index plunged again Thursday, triggering the second automatic halt in trading this week.

The price of oil sank to its lowest level in 12 years as traders worried that a slump in China, the world's second-largest economy, would mean lower global demand for energy.

The Dow Jones industrial average sank 275 points, or 1.6 percent, to 16,637 as of 9:35 a.m. Eastern time.

The Standard & Poor's 500 index lost 30 points, or 1.5 percent, to 1,960. The Nasdaq composite fell 89 points, or 1.9 percent, to 4,746.

Oil and gas companies again fell more than the rest of the market as energy prices continued to plunge. Ensco dropped 5 percent.