The recent improvement in the nation’s job market slowed substantially in March as employers expanded payrolls by 120,000 jobs, the Labor Department reported Friday.

The number of new jobs fell far below economists’ estimates and marked the first time since November that employers added fewer than 200,000 jobs. Despite the disappointing numbers, the nation’s unemployment rate ticked down to 8.2 percent.

Some analysts called the slowdown in hiring the result of an unusually warm winter that caused seasonal work, such as outdoor construction, to continue apace instead of slowing.

“The unusually warm winter likely shifted some hiring into the first two months of the year,” wrote Sophia Koropeckyj, managing director of Moody’s Analytics.

Others, including Federal Reserve Chairman Ben S. Bernanke, worried that the sharp decline in joblessness — the unemployment rate has dropped from a recent high of 9.1 percent in August — was not supported by underlying economic growth. The decline has been “somewhat out of sync” with the rather modest pace of economic growth, Bernanke said this month.

Even at the recent pace of more than 200,000 jobs a month, the nation was not expected to return to full employment for more than five years, economists have said.

With the nation’s still-troubled job market sure to be at the center of this year’s presidential campaign, GOP front-runner Mitt Romney was quick to criticize President Obama for the tepid job creation in March.

“This is a weak and very troubling jobs report that shows the employment market remains stagnant,” Romney said in a statement. “Millions of Americans are paying a high price for President Obama’s economic policies, and more and more people are growing so discouraged that they are dropping out of the labor force altogether.”

The White House, meanwhile, was careful to point out that the nation is still dealing with the aftereffects of the severe economic downturn that took hold long before Obama was in office.

“There is more work to be done, but today’s employment report provides further evidence that the economy is continuing to recover from the worst economic downturn since the Great Depression,” said Alan B. Krueger, chairman of the Council of Economic Advisers. “It is critical that we continue to make smart investments that strengthen our economy and lay a foundation for long-term middle-class job growth so we can continue to dig our way out of the deep hole that was caused by the severe recession that began at the end of 2007.”

Many economists, pointing to a decline in jobless claims and a surge in retail sales, the stock market and consumer confidence, had expected March job creation to top 200,000 for the fourth consecutive month.

“The low job growth in March was an unpleasant surprise and underscores the fact that a robust jobs recovery has not yet solidified,” said Heidi Shierholz, an economist at the Economic Policy Institute.

The jobs report showed that retail employment declined by 34,000 in March, while employment increased in manufacturing, health care and leisure and hospitality.

The extremely high jobless rates that African Americans and Hispanics have endured for years continued last month, with unemployment at 14 percent among black people and at 10.3 percent among Hispanics , the government reported.

The jobs report also showed little change in the plight of workers who have been out of work for six months or more. The number of long-term unemployed was essentially unchanged at 5.3 million, and they account for 42.5 percent of the overall nation’s jobless population, the report said.

“While the slight decline in the unemployment rate and downward trend in the number of workers filing for unemployment are welcome news, the slower than anticipated job growth for March is worrisome,” Christine Owens, executive director of the National Employment Law Project, said in a statement. “We should not attach too much significance to one month’s numbers, especially in light of overall positive trends, but there’s no question that the persistence of a deep jobs deficit along with low labor force participation rates and the lopsided growth in low-wage jobs remain a cause for concern about how robust and sustainable the recovery will be.”