Initial jobless claims surged in the Feb. 21 week, up 31,000 to a 313,000 level, the biggest percentage increase since 2013.
Continuing claims dropped modestly but remain up around 3.5% over the last quarter - near the worst since 2009.
Data on continuing claims, which are reported with a 1-week lag, are mixed. Continuing claims for the February 14 week fell 21,000 to 2.401 million but the 4-week average rose 2,000 to 2.399 million.
The unemployment rate for insured workers is unchanged at a recovery low of 1.8%.