The number of U.S. workers filing new claims for unemployment insurance unexpectedly rose to its highest level in close to six months, a fresh signal of a weak jobs market.

The number of new claims for jobless benefits rose 2,000 to 484,000 in the week ended August 7, the second straight increase, Labor Department data showed on Thursday.

This is not a good number, said John Brady, an analyst at MF Global in Chicago. Claims are going the wrong way. That has the market concerned.

The data comes two days after the Federal Reserve downgraded its assessment of the economy's health and said it would take steps to ensure its support for the fragile economic recovery does not wane.

U.S. stock index futures added to losses, while U.S. Treasury debt prices pared losses following the data.

The jobless claims data is the latest in a series of releases which indicate the pace of the economic recovery is slowing.

Economists have been ratcheting down estimates for second-quarter economic growth after data on trade and inventories for June suggested it was not as strong as earlier thought.

The government estimated last month the economy advanced at a 2.4 percent annualized pace in the April-June quarter, far more slowly than the 3.7 percent pace of the first quarter, and now some economists believe the economy may have grown at less than half that rate.

The Labor Department said separately that higher oil prices pushed prices for imported goods higher in July for the first time in three months, though at half the pace economists had expected.

Import prices rose 0.2 percent in July after falling 1.3 percent in June and a revised 0.8 percent in May. That left the three-month cumulative total down 2.0 percent, the largest decline since the three months ended February 2009.

Economists polled by Reuters had expected import prices to rise 0.4 percent in July.

The four-week moving average of unemployment claims, which economists prefer because it smoothes out weekly fluctuations, rose 14,250 to 473,500, also the highest level since the week ended February 20.

Economists polled by Reuters had expected claims in the latest week to fall to 465,000 from the previously reported 479,000.

The number of people still collecting unemployment benefits after an initial week of aid in the week ended July 31 fell 118,000 to 4.45 million, the lowest level since late June. Economists had expected 4.53 million. The four-week moving average of continuing claims fell 64,500 to 4.52 million, the lowest level since December 2008.

Prices for exported goods unexpectedly fell 0.2 percent in July after falling a revised 0.7 percent in the prior month. The Reuters poll showed economists expecting a 0.1 percent increase in July.

Oil import prices rose 2.0 percent last month after falling for two months while prices excluding oil fell 0.2 percent.

(Reporting by Corbett B. Daly; Additional reporting by Ryan Vlastelica in New York; Editing by Andrea Ricci)