The number of people filing initial applications for U.S. state unemployment benefits rose unexpectedly last week, but the underlying trend continued to point to a strengthening labor market, the government reported Thursday. The Labor Department said jobless claims rose 6,000 to 278,000 last week, in contrast to economist expectations for a decline. Claims now have been below the 300,000 level—associated with healthy labor-market conditions—for a full year, the longest such period since the early 1970s. The four-week moving average of jobless claims—a less volatile measure considered a better gauge of labor-market trends—fell 1,750 to 270,250 last week, the lowest level since late November. The strength in the labor market also was supported by another report Thursday showing announced layoffs by U.S. companies fell 18 percent in February. The consultancy firm said layoffs remained concentrated in the energy sector, which has been hurt by the plunge in crude-oil prices. Energy employers announced more than 25,000 job cuts last month. There also was an increase in layoffs in the technology sector, which the company said was normal due to the "constant reinvention" in the industry.