CHICAGO — It sounds like an oxymoron, but the concept of working in retirement is fast becoming the norm for many older Americans — forced by dwindling financial resources and a recessionary economy to stay in or return to the job market.

Longer lifespans and a desire to remain productive and connected already had begun pushing the number of older workers higher. Now the financial crisis is accelerating interest in working later, with career sites and organizations for seniors and older workers reporting a surge in job-hunting efforts.

Sixty-three-year-old Marian Austin of Alfred, Maine, is among those who need to work again just to make ends meet in retirement. In this economy, her late ex-husband's Social Security isn't nearly enough.

"It's been difficult," said the former gift shop owner and retail manager, who retired two years ago. "I don't know how I will pay for fuel oil for heating. I can't walk into a grocery store and buy what I want. I don't look forward to Christmas, because I can't buy gifts this year."

AARP, the nation's largest advocacy group for older Americans, saw dramatic evidence of the trend in September, when more than 2,000 people attended its annual job fair in Washington, D.C., more than double the previous year's attendance. The job-seekers included many who had been recently laid off and retirees worried about the economy and the pressure on their limited resources.

"We've definitely seen an increase in the sense of urgency in terms of jobs," said Deborah Russell, the organization's director of work-force issues.

A market for retirement jobs essentially emerged a decade or so ago. Now, postings for those at or approaching retirement age are an important and growing phenomenon in the labor market, as evidenced by online job boards that include RetirementJobs.com, RetireeWorkforce.com and Seniors4Hire.org, which cater to not just retirees but anyone 50 and older.

Demand for such resources is only likely to grow with the graying of the work force expected to continue. Workers age 65 and over are expected to account for 6.1 percent of the labor force by 2016, up sharply from 3.6 percent in 2006, according to the U.S. Bureau of Labor Statistics.

"For decades, we've been making it easier for people to get out of the labor market," said Marc Freedman, CEO of Civic Ventures, which focuses on helping older baby boomers launch second careers involving social contribution. "Now, there's a growing need in the opposite direction."