WASHINGTON — Initial jobless claims unexpectedly jumped last week to the highest level since March, the Labor Department said Thursday, countering recent upbeat economic data and reflecting holiday season volatility.

The number of people filing for unemployment benefits for the first time rose to 379,000 from the previous week's upwardly revised level of 369,000. Analysts had projected claims to drop to about 337,000.

The end-of-the-year holidays cause big swings in claim levels, adding to the volatility of the weekly claims data, economists said.

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"Given the usual issues surrounding seasonality adjustments this time of year, it is important to take this report with a grain of salt, and the next several reports as well until we get clean data after the new year," said Lindsey Piegza, chief economist at brokerage firm Sterne Agee.

The four-week average, which smooths out some of the fluctuations, rose to 443,500 last week. That was an increase of 13,250 from the previous week and brings the rolling average close to the important 350,000 level. Weekly claims below that level indicate moderate growth in the labor market. A rise in the four-week average above 350,000 would be a worrisome sign for an economic recovery that has appeared to be gaining momentum.

Job creation has been improving in recent months, averaging 204,000 from August through November. The unemployment rate dropped to 7% last month, the lowest in five years.

The strengthening labor market and other positive economic indicators led Federal Reserve policymakers on Wednesday to vote to start dialing back a key stimulus program.

Beginning next month, the Fed will reduce its monthly bond purchases to $75 billion from the $85 billion in place since September 2012.

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