At a time of growing tensions involving Muslims in the United States, a record number of Muslim workers are complaining of employment discrimination, from co-workers calling them "terrorist" or "Osama" to employers barring them from wearing head scarves or taking prayer breaks.

Such complaints were increasing even before frictions erupted over the planned Islamic center in Lower Manhattan, with Muslim workers filing a record 803 such claims in the year ended Sept. 30. That was up 20 percent from the previous year and up nearly 60 percent from 2005, according to federal data.

The number of complaints filed since then will not be announced until January, but Islamic groups say they have received a surge in complaints recently, suggesting that 2010’s figure will set another record.

The federal Equal Employment Opportunity Commission has found enough merit in some of the complaints that it has filed several prominent lawsuits on behalf of Muslim workers.

In August, the commission sued the meat-packing company JBS Swift on behalf of 160 Somali immigrants, saying supervisors and workers had cursed them for being Muslim; thrown blood, meat and bones at them; and interrupted their prayer breaks.

On Sept. 1, the commission filed a case against Abercrombie & Fitch, the fashionable clothing retailer, accusing it of discrimination for refusing to hire an 18-year-old Muslim because she was wearing a head scarf.

And in June, the agency sued a Four Points by Sheraton hotel in Phoenix, asserting that its management had illegally permitted a hostile work environment in which workers called an Iraqi immigrant a "camel jockey," mocked him with Arab ululations and taunted him over news items about captured terrorists. (The hotel’s manager said many of the claims were untrue.)

"There’s a level of hatred and animosity that is shocking," said Mary Jo O’Neill, regional attorney of the EEOC’s Phoenix office. "I’ve been doing this for 31 years, and I’ve never seen such antipathy toward Muslim workers."

Although Muslims make up less than 2 percent of the U.S. population, they accounted for about one-quarter of the 3,386 religious discrimination claims filed with the EEOC last year. Complaints filed by Jews rose slightly in fiscal 2009, while complaints filed by Catholics, Protestants, Sikhs and Seventh-day Adventists declined. Claims of race, sex and age discrimination also fell. The rising number of complaints by Muslims, which exceeds even the amount filed in the year after the terrorist attacks of. Sept. 11, 2001, comes as tensions rise between Muslim Americans and those of other faiths.

Polls have shown that many Americans feel a growing wariness toward Muslims after the 9/11 attacks and after years of fighting in Iraq and Afghanistan. Mosques and Islamic community centers in the United States – most prominently one proposed near ground zero in Manhattan – have faced substantial opposition. And a Florida pastor received national attention this month for threatening to burn the Quran on Sept. 11.

"We can go back in history and find other times when there were hot emotional and political tensions over religion," said Michael J. Zimmer, co-author of several books on employment discrimination and a law professor at Loyola University in Chicago. "Right now, there is a lot of heat as to the Muslims."

Mohammad Kaleemuddin, a Pakistani immigrant who drove trucks for the U.S. war effort in Iraq for three years, said that while he was working for a construction company in Houston, his supervisor and several co-workers called him "Osama," "al Qaeda," "Taliban," and "terrorist."

"It was very rough," said Kaleemuddin, who was fired after protesting to management about the ethnic slurs. "It brought a bit of terror in my chest. I’d wonder, ‘Why are they doing this? I’ve always been nice to them."’

After he filed a complaint, the EEOC sued the company he worked for, Pace Services. The company agreed in April to pay him $61,250 to settle the case.

Kaleemuddin became a U.S. citizen in 2002 and had worked for three years as a truck driver in Iraq helping the U.S. war effort.

"This is my country, and it doesn’t matter how much they hate me," he said. "I’m not going to hate my country."

Experts on religion and employment discrimination say many factors are behind this surge in discrimination claims.

"In America right now, there are intense concerns about many issues – immigration, the faltering economy, the interminable wars" and the erroneous belief, held by many Americans, that the first nonwhite president is Muslim, said Akbar Ahmed, a professor of Islamic studies at American University.

"In all of these, there’s one link, Islam. Islam is the lightning rod. Whenever there is a great distrust or antipathy, it spills beyond religion into public life," the professor said.

Ahmed said that Muslims in the United States were generally reluctant to stick their necks out and complain about discrimination, partly in the belief that attitudes toward them will gradually improve. But he said that growing intolerance has prompted more Muslims to stand up for their rights and file EEOC complaints.

Workers have complained of discrimination even in regions known for their diversity.

Halla Banafa filed a claim with the commission after she was turned down at age 18 for a job stocking merchandise at an Abercrombie Kids store in Milpitas, Calif. According to the EEOC, the manager made a note of "not Abercrombie look" on the interview form.

"I never imagined anyone in the Bay Area would reject me because of my head scarf," Banafa said.

Federal law requires employers to accommodate head scarves, also called hijabs, as well as prayer breaks and other practices based on sincere religious beliefs unless doing so would impose an undue hardship on the employer.

"Abercrombie just decided they’re not going to comply with the law requiring religious accommodation," said William R. Tamayo, regional attorney of the commission’s San Francisco office. "Here she was going to wear a hijab to basically stock things in the back. Their intolerance is off the charts."

Last year, the commission also sued Abercrombie for refusing to hire a 17-year-old wearing a hijab at a store in Tulsa, Okla.

Ronald A. Robins Jr., Abercrombie’s general counsel, said the company disputed both claims, adding that the retailer "makes every reasonable attempt to accommodate the religious practices of associates and applicants, including, when appropriate, allowing associates to wear a hijab."

In 2004, Abercrombie agreed to pay $40 million to settle an EEOC lawsuit charging it with racial bias against Asian, black and Hispanic employees, many of whom said they had been steered to low-visibility, back-of-the-store jobs.

At Swift, the meatpacker, the charge of discrimination dates to 2008, when Somali workers complained that the restroom had profanity-laced anti-Muslim graffiti, that their prayer breaks were often interrupted and that the company would not move their meal breaks to right after sundown during the month of Ramadan, when Muslims fast during the day. After Muslim employees staged a walkout, the company fired all the protesters, the commission said.

"The antipathy was pretty stark," said the EEOC’s O’Neill. "Not only were they denied reasonable accommodations, they were called awful, awful names."

Chandler Keys, a Swift spokesman, declined to discuss the lawsuit but said that since 2008, the company has had no similar incidents.

"We’ve worked closely and diligently with the East African community and other groups to avoid a recurrence of such problems," he said.

Sometimes sharp disputes arise over whether employers have done enough to accommodate Muslim employees.

Imane Boudlal, a 26-year-old from Casablanca, Morocco, had worked for two years as a hostess at the Storytellers Cafe at Disneyland in Anaheim, Calif., when she decided she would begin wearing her hijab at work during Ramadan last month. Boudlal said her supervisors told her that if she insisted on wearing the scarf, she could work either in back or at a telephone job. She refused and has not worked while the dispute continues.

Disney officials said her head scarf clashed with the restaurant’s early-1900s theme, and they proposed a period hat with some scarf that would fall over her ears. Boudlal rejected that as un-Muslim.

"They wanted to hide the fact that I looked Muslim," she said.

Michael Griffin, a Disney spokesman, said the company’s "cast members" agree to comply with its appearance guidelines.

"When cast members request exceptions to our policies for religious reasons, we strive to make accommodations," he said, adding that Disney has accommodated more than 200 such requests since 2007.