WASHINGTON - The number of U.S. workers filing new applications for unemployment insurance unexpectedly surged last week, while producer prices increased sharply in January, raising potential hurdles for the economic recovery.

Initial claims for state unemployment benefits increased 31,000 to 473,000, the Labor Department said on Thursday. That compared to market expectations for 430,000.

Another report from the department showed prices paid at the farm and factory gate rose a faster than expected 1.4 percent from December after a 0.4 percent gain in December, as higher gasoline prices and unusually cold temperatures helped boost energy costs.

When you have PPI moving up and still no progress in the jobs situation, that doesn't bode well for continued improvement in equity prices, said Alan Lancz, president at Alan B. Lancz & Associates Inc in Toledo, Ohio.

U.S. stock index futures added to losses after jobless claims and producer price data, while government debt prices rose.

Last week was the survey week for the employment report for February, which is scheduled for release in early March.

The labor market, hardest hit by the worst recession in seven decades, has lagged the economic recovery that started in the second half of 2009. The economy has lost 8.4 million jobs since the start of the downturn in December 2007.

The PPI report may give investors, who keeping a wary eye on inflation following massive efforts by the Federal Reserve to pull the economy out of its worst slump since the Great Depression of the 1930s, something to worry about.

The bottom line is that the Fed is going to have some decisions to make at its next meeting, since it seems inflation is now back on the table, said Lancz.

Fed officials, keeping an eye on how quickly the recovering economy absorbs the excess slack that built up during the recession, have said they are likely to keep interest rates extraordinarily low for an extended period.

About three-fourths of the increase in PPI last month was due to a 5.1 percent jump in prices for energy goods, the department said. Energy costs were pushed up by a spike in prices for gasoline, liquefied petroleum and home heating oil.

Strong energy prices overshadowed a slowdown in the food prices, which rose 0.4 percent after increasing 1.3 percent in December.

Stripping out the volatile food and energy costs, core producer prices rose a faster than expected 0.3 percent last month after being flat in December. The core index had been forecast to rise 0.1 percent in January.

The department on Friday will release its consumer price report for January. Headline CPI is seen rising 0.3 percent from December and core CPI gaining 0.1 percent, according to a Reuters survey.

It does present some upside risks to our call for only modest gains in CPI and also points to some possible upward price pressures in the pipeline, Millan Mulraine, an economics strategist at TD Securities in Toronto.

In the claims report, the four-week moving average of new claims, which irons out week-to-week volatility, fell 1,500 to 467,500, the Labor Department said. The number of people still receiving for benefits after an initial week of aid was unchanged at 4.56 million in the week ended February 6.

This measure has held below the 5 million mark for eight straight weeks and analysts believe it is starting to reflect an improvement in the labor market rather than people merely dropping off rolls because they have exhausted their benefits.

(Reporting by Lucia Mutikani; Editing by Neil Stempleman)

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