WASHINGTON -- The number of U.S. workers filing new claims for jobless benefits unexpectedly rose last week, a government report showed on Thursday, as companies continued to cut payrolls amid uncertainty over the economic outlook.

Initial claims for state unemployment insurance benefits rose 15,000 to a seasonally adjusted 576,000 in the week ended Aug. 15 from 561,000 the prior week, the Labor Department said.

Analysts polled by Reuters had forecast new claims slipping to 550,000 last week from a previously reported 558,000. A Labor Department official said there were no special factors influencing the report.

The number of people collecting long-term unemployment benefits edged up 2,000 to 6.24 million in the week ended Aug. 8, the latest week for which the data is available. However, the four-week moving average declined 2,500 to 6.27 million.

The insured unemployment rate, which measures the percentage of the insured labor force who are jobless, was unchanged at 4.7 percent.

The four-week moving average for new claims climbed 4,250 to 570,000 last week. The four-week moving average is considered a better gauge of underlying trends as it irons out week-to-week volatility.