WASHINGTON — A surprisingly weak jobs report for a second straight month has renewed concern that the U.S. economy might be slowing after a strong finish last year.

Employers added 113,000 jobs in January, far fewer than the average monthly gain of 194,000 last year. Job gains have averaged just 154,000 the past three months, down from 201,000 in the preceding three.

The sluggish job growth could undermine hopes that economic growth will accelerate this year. But economists also say they expect hiring to return to healthier levels in coming months. They note that solid job gains in January in manufacturing and construction point to underlying strength.

The government said Friday that manufacturers, construction firms and mining and drilling companies added a strong 76,000 jobs combined.

“You rarely see expansions in these industries without the economy being in fairly healthy shape,” said Gary Burtless, an economist at Brookings Institution.

And more people began looking for work in January, a sign that they were optimistic about finding jobs. Some of these people found work, thereby reducing the unemployment rate to 6.6 percent from 6.7 percent in December. That’s the lowest rate since October 2008.

Investors seemed generally pleased by the figures. The Dow Jones industrial average rose 78 points early in the day, before paring its gains by midmorning.

Cold weather likely held back hiring in December, economists said, but the impact faded in January. Construction firms, which sometimes stop work in bad weather, added 48,000 jobs last month.

Over the past month, signs of economic weakness in the United States and overseas have sent stock prices sinking. Upheaval in developing countries has further spooked investors.

The anxiety marks a reversal from just a few weeks ago, when most analysts were increasingly hopeful about the global economy. U.S. growth came in at a sturdy 3.7 percent annual pace in the second half of last year. The Dow finished 2013 at a record high. Europe’s economy was slowly emerging from a long recession. Japan was finally perking up after two decades of stagnation.