U.S. stocks fell on Thursday as the number of first-time claims for jobless benefits rose unexpectedly, highlighting the bumpy ride for employment as economic growth picks up.

Weekly initial unemployment claims posted their biggest jump in six months, suggesting that despite signs of economic improvement, the labor market still faces headwinds. In a potentially encouraging sign, however, continuing claims retreated sharply to 3.88 million from 4.13 million.

Because continued claims improved, and because we've certainly seen some progress in labor market data generally over recent weeks, there's a bit of willingness to look past the disappointing initial claims number, said Bruce McCain, chief investment strategist at Key Private Bank in Cleveland, Ohio.

Producer prices rose more than expected in December as energy and food costs surged. Underlying inflation remained subdued.

The Dow Jones industrial average <.DJI> was down 13.78 points, or 0.12 percent, at 11,741.66. The Standard & Poor's 500 Index <.SPX> was down 1.55 points, or 0.12 percent, at 1,284.41. The Nasdaq Composite Index <.IXIC> was down 5.76 points, or 0.21 percent, at 2,731.57.

Marathon Oil Corp rose 8 percent to $43.77 after it said it would spin off its refinery and pipeline operations into a stand-alone company.

Williams-Sonoma Inc raised its fourth-quarter outlook after a strong holiday season as margins improved, but the stock fell 3.4 percent to $33.03 as some analysts said the company's pace of growth was moderating.

Intel Corp is scheduled to report its quarterly results after the market closes. Its shares dipped 0.2 percent to $21.25.

Spain followed Portugal with a successful debt sale on Thursday, and investors showed growing confidence that governments would agree to new measures to stem the debt crisis.

(Editing by Padraic Cassidy)

Portugal