WASHINGTON - The number of Americans initially applying for unemployment aid last week rose again after dropping for two weeks, signaling that the job market recovery is still fragile, the US Labor Department reported Thursday.

The Labor Department said that the advance figure for seasonally adjusted initial claims for jobless benefits was 424,000 in the week ending May 21, an increase of 10,000 from the prior week's revised figure. It was also the first increase in the past three weeks.

Fewer than 425,000 people applying for aid is consistent with modest job growth, but the number of jobless claims will have to fall to 375,000 or below to signal a sustained drop in the unemployment rate.

However, the four-week moving average, a more closely watched claims figure, dipped slightly to 438,500, a decrease of 1,750 from the previous week's revised average.

The advance figure for seasonally adjusted insured unemployment during the week ending May 14 was 3.69 million, a sharp decrease of 46,000 from the previous week.

In addition, the US economy rose at an annual rate of 1.8 percent in the first quarter of 2011, much weaker than last quarter, according to the second estimate of the government report released on Thursday.

The weekly figures of jobless benefits application reflect the level of layoffs and indicate real-time condition of the American job market.