The U.N. Human Rights Committee said poor and black Americans were "disadvantaged" after Katrina, and the U.S. should work harder to ensure that their rights "are fully taken into consideration in the reconstruction plans with regard to access to housing, education and health care."
The United States said federal and Louisiana state authorities were examining many of the issues raised by the committee.
In New Orleans, activists praised the U.N. report at a news conference in the predominantly black Gert Town neighborhood, which remains heavily damaged by the hurricane.
Monique Harden, co-director of Advocates for Environmental Human Rights, urged the U.N. to examine the treatment of black and poor Gulf Coast residents, and said the committee's findings were important to recovery efforts in the region.
"It's a wake-up call, and it's also a call for change in the way the United States government has been handling this recovery," Harden said.
She and other advocates said former residents continue to fight for a chance to return to the city, where housing shortages have kept away many lower-income people.
"The United States has to do something more than just show itself once and while," said Ronald Chisom of the People's Institute for Survival and Beyond.
Harden said that, although the committee has little power to force the U.S. government to make changes, she believes that such reports can improve human rights by influencing U.S. decision-makers.
"We believe having the U.N. on our side will have a tremendous effect on turning the U.S. government around," she said.
The U.N. panel said it wants to be informed of the results of inquiries into the alleged failure to evacuate inmates from a prison, and into allegations that authorities did not allow New Orleans residents to cross a bridge into Gretna, La.
It offered no further specifics about problems it found with the Katrina response, or possible solutions.
"I think the president and everyone in the United States said that Katrina was something that no one was entirely prepared for and it did raise huge challenges for the United States," said Robert Harris, of the office of the Legal Adviser of the U.S. State Department. "We're looking at a large list of lessons from Katrina and trying to make sure that the next time, God forbid something like that happens, we are better prepared."
The panel of 18 independent experts, which reviews the practices of the 156 countries who have ratified the 1966 International Covenant on Civil and Political Rights, said it was concerned about information that blacks and poor people "were disadvantaged by the rescue and evacuation plans implemented when Hurricane Katrina hit."
Criticism by the panel brings no penalties beyond international scrutiny.
The Katrina findings comprised two paragraphs in a 12-page release of findings that also included recommendations on U.S. policies in the war on terror.
The U.S. mission to the U.N.'s European headquarters in Geneva criticized the committee's examination of many issues it said were outside the scope of its mandate, particularly dealing with the war on terrorism.
But on domestic issues, it said "the committee has made recommendations in matters under its competence, including efforts to address race and sex discrimination, capital punishment, the aftermath of Hurricane Katrina, and voting rights."
The committee also addressed reports of de facto racial segregation in public schools.