Demolition began on Wednesday night at one housing project that had been scheduled to be destroyed before the storm and will begin on two other projects this weekend.

Federal officials say the barracks-style complexes were substandard before Hurricane Katrina and were badly damaged by the storm. New subsidized housing, and vouchers for existing and new apartments, will ensure that no one who lived in the demolished projects will be left homeless, they said.

“The goal was to rebuild it, build it better, and move people into new homes,” said Jereon M. Brown, a spokesman for the housing department.

Mr. Brown said of the protesters: “Ask how many of them have lived in public housing, have been to public housing other than to protest.”

But the protesters, including some former residents of the projects, say the sturdy apartment buildings could be rehabilitated, especially at a time when little low-cost housing is available in New Orleans.

Hurricane Katrina destroyed more than 50,000 rental units here, and damaged thousands more apartments, affecting two-thirds of the city’s rental stock. Rents have soared for the apartments that remain habitable.

Adding to the pressure on the rental market, almost 3,000 families living in government trailer parks in Louisiana must find a new place to live in the next few months, as the Federal Emergency Management Agency closes the sites it manages. By the end of the year, it will stop paying for 3,700 trailers in private trailer camps.