WASHINGTON — New claims for US unemployment insurance benefits surged more than expected last week to the highest level since January, official data showed Thursday.

The Labor Department reported initial jobless claims rose to a seasonally adjusted 429,000 in the week ending April 23.

That was sharply higher than the average analyst estimate of 390,000.

The Labor Department revised slightly upward the prior week's claims number to 404,000.

The department gave no explanation for the unexpected rise in the weekly indicator on the jobs market.

The four-week moving average, which helps to smooth volatility, was 408,500 claims, an increase of 9,250 from the prior week. The average had been below the 400,000 threshold for eight consecutive weeks.

The US unemployment rate fell to 8.8 percent in March, its lowest level in two years, as the economy struggles to recover from recession.