NEW YORK (AP)--U.S. stocks are opening lower as investors fret about signs of belligerence in North Korea and more weakening of China's economy.

Markets were already lower in Asia and Europe by the time trading began in the U.S. after North Korea claimed to have conducted a test of a hydrogen bomb.

Oil prices fell sharply after China reported that its service sector continued to weaken. That could mean lower demand for energy in the world's second-largest economy.

The Dow Jones industrial average dropped 229 points, or 1.4 percent, to 16,930 as of 9:35 a.m. Eastern time.

The Standard & Poor's 500 index lost 25 points, or 1.3 percent, to 1,992. The Nasdaq gave up 60 points, or 1.3 percent, to 4,830.

Bond prices rose. The yield on the 10-year Treasury note fell to 2.19 percent.

--Associated Press