The number of Americans filing for unemployment benefits bounced back from a 42-1/2-year low last week, but the underlying trend remained consistent with tightening labor market conditions.

Initial claims for state unemployment benefits increased 9,000 to a seasonally adjusted 257,000 for the week ended April 23, the Labor Department said on Thursday.

Claims for the prior week were revised to show 1,000 more applications than previously reported.

Economists polled by Reuters had forecast claims rising to 260,000 in the latest week. Jobless claims have now been below 300,000, a threshold associated with healthy labor market conditions, for 60 weeks, the longest stretch since 1973.

A Labor Department analyst said there were no special factors influencing last week's claims data and no states had been estimated.

The four-week moving average of claims, considered a better measure of labor market trends as it irons out week-to-week volatility, fell 4,750 to 256,000 last week, the lowest since December 1973.

The number of people still receiving benefits after an initial week of aid decreased 5,000 to 2.13 million in the week ended April 16, the lowest since November 2000.

The four-week average of the so-called continuing claims declined 10,500 to 2.16 million, the lowest reading since November 2000. The continuing claims data covered the survey week for April's unemployment rate.

The four-week average of continuing claims fell 47,750 between the March and April survey periods, suggesting an improvement in the unemployment rate. The jobless rate was at 5.0 percent in March.