The number of Americans initially applying for unemployment aid last week declined to the lowest level in a little more than four years, signaling a strengthening labor market, the U.S. Labor Department reported Thursday.

The Labor Department said that the advance figure for seasonally adjusted initial claims for jobless benefits was 348,000 in the week ending March 17, a decrease of 5,000 from the previous week's revised figure.

The fresh figure hit a four-year low, which was the fewest since February 2008. After three consecutive months of improvement in job market, the reading indicated the momentum may be maintained for another one.

As a rule of thumb, fewer than 425,000 people applying for aid was consistent with modest job growth, and the number of jobless claims below 375,000 indicated a sustained drop in the unemployment rate.

Meanwhile, the four-week moving average, which helps smooth out week-to-week volatility, edged down by 1,250 to 355,000, near a four-year low.

The advance figure for seasonally adjusted insured unemployment during the week ending March 10 was 3.352 million, a decrease of 9,000 from one week earlier.

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