Worries about higher inflation and signs of job market weakness prompted investors to sell stocks on Thursday.

Government data showed weekly jobless claims rose unexpectedly, climbing back above 400,000, while U.S. core producer prices rose slightly faster than expected in March, pointing to increased inflation pressures.

Improvement in the jobs market has had a hard time gaining traction, while commodity prices have clouded the outlook, said Peter Boockvar, equity strategist at Miller Tabak & Co in New York.

It's worth speculating that the persistent rise in energy prices, among other commodity prices, and the fallout from the Japanese earthquake both are impacting the psyche of the average CEO ... and may be impacting the appetite to expand until these factors get some clarity, Boockvar said.

Google is scheduled to release results after markets close on Thursday, with analysts expecting to see a 25 percent year-on-year increase in net revenue to $6.32 billion and earnings per share of $8.10, up from $6.76 a year earlier. Google shares were down 0.7 percent at $572.15.

The Dow Jones industrial average <.DJI> was down 77.38 points, or 0.63 percent, at 12,193.61. The Standard & Poor's 500 Index <.SPX> was down 8.72 points, or 0.66 percent, at 1,305.69. The Nasdaq Composite Index <.IXIC> was down 22.04 points, or 0.80 percent, at 2,739.48.

(Reporting by Angela Moon, Editing by Kenneth Barry)