NEW ORLEANS, Sept. 1 - Despair, privation and violent lawlessness grew so extreme in New Orleans on Thursday that the flooded city's mayor issued a "desperate S O S" and other local officials, describing the security situation as horrific, lambasted the federal government as responding too slowly to the disaster.

Thousands of refugees from Hurricane Katrina boarded buses for Houston, but others quickly took their places at the filthy, teeming Superdome, which has been serving as the primary shelter. At the increasingly unsanitary convention center, crowds swelled to about 25,000 and desperate refugees clamored for food, water and attention while dead bodies, slumped in wheelchairs or wrapped in sheets, lay in their midst.

"Some people there have not eaten or drunk water for three or four days, which is inexcusable," acknowledged Joseph W. Matthews, the director of the city's Office of Emergency Preparedness.

"We need additional troops, food, water," Mr. Matthews begged, "and we need personnel, law enforcement. This has turned into a situation where the city is being run by thugs."

Three days after the hurricane hit, bringing widespread destruction to the Gulf Coast and ruinous floods to low-lying New Orleans, the White House said President Bush would tour the region on Friday. Citing the magnitude of the disaster, federal officials defended their response so far and pledged that more help was coming. The Army Corps of Engineers continued work to close a levee breach that allowed water from Lake Pontchartrain to pour into New Orleans.

The effects of the disaster spilled out over the country. In Houston, the city began to grapple with the logistics of taking tens of thousands of refugees into the Astrodome. American Red Cross officials said late Thursday night that the Astrodome was full after accepting more than 11,000 refugees and that evacuees were being sent to other shelters in the Houston area.

Elsewhere, San Antonio and Dallas each braced for the arrival of 25,000 more, and Baton Rouge overnight replaced New Orleans as the most populous city in Louisiana and was bursting at the seams.

The devastation in the Gulf Coast also continued to roil oil markets, sending gasoline prices soaring in many areas of the country. In North Carolina, Gov. Michael F. Easley called on citizens to conserve fuel while two big pipelines that supply most of the state's gasoline were brought back on line.

Throughout the stricken region, scores of frantic people, without telephone service, asked for help contacting friends or relatives whose fates they did not know. Some ended up finding them dead. Others had emotional reunions. Newspapers offered toll-free numbers or Web message boards for the searches.

Meanwhile, the situation in New Orleans continued to deteriorate. Angry crowds chanted cries for help, and some among them rushed chaotically at helicopters bringing in food. Although Mayor C. Ray Nagin speculated that thousands might have died, officials said they still did not have a clear idea of the precise toll.

"We're just a bunch of rats," said Earle Young, 31, a cook who stood waiting in a throng of perhaps 10,000 outside the Superdome, waiting in the blazing sun for buses to take them away from the city. "That's how they've been treating us."

Chaos and gunfire hampered efforts to evacuate the Superdome, and, Superintendent P. Edward Compass III of the New Orleans Police Department said, armed thugs have taken control of the secondary makeshift shelter at the convention center. Superintendent Compass said that the thugs repelled eight squads of 11 officers each he had sent to secure the place and that rapes and assaults were occurring unimpeded in the neighboring streets as criminals "preyed upon" passers-by, including stranded tourists.

Mr. Compass said the federal government had taken too long to send in the thousands of troops - as well as the supplies, fuel, vehicles, water and food - needed to stabilize his now "very, very tenuous" city.

Col. Terry Ebbert, director of homeland security for New Orleans, concurred and he was particularly pungent in his criticism. Asserting that the whole recovery operation had been "carried on the backs of the little guys for four goddamn days," he said "the rest of the goddamn nation can't get us any resources for security."

"We are like little birds with our mouths open and you don't have to be very smart to know where to drop the worm," Colonel Ebbert said. "It's criminal within the confines of the United States that within one hour of the hurricane they weren't force-feeding us. It's like FEMA has never been to a hurricane." FEMA is the Federal Emergency Management Agency.

Federal officials took pains to defend their efforts, maintaining that supplies were pouring into the area even before the hurricane struck, that thousands of National Guard members had arrived to help secure the city and that thousands more would join them in coming days.

Gov. Kathleen Babineaux Blanco of Louisiana said some 300 National Guard members from Arkansas were flying into New Orleans with the express task of reclaiming the city. "They have M-16's and they are locked and loaded," she said.

Speaking at a news conference in Washington, Michael Chertoff, the secretary of homeland security, said that the Superdome had "crowd control issues" but that it was secure. He referred to what he called "isolated incidents of criminality" in the city.

Mr. Chertoff said Hurricane Katrina had presented a "double challenge" because it was really two disasters in one: the storm and then the flooding.

"For those who wonder why it is that it is difficult to get these supplies and these medical teams into place, the answer is they are battling an ongoing dynamic problem with the water," he said.

On Thursday, the Army Corps of Engineers was battling the water problem by finishing a metal wall across the mouth of the 17th Street Canal, the source of most of the flooding. Once finished, the wall was expected to staunch the flow from Lake Pontchartrain into the canal, which would allow engineers to repair a breach in the levee and to start pumping water from the city.

The federal government's other priority was to evacuate New Orleans, Mr. Chertoff said. To that end, some 200 buses had left the Superdome for the Astrodome in Houston by midday, he said, adding that another 200 buses were expected to start loading passengers later Thursday and that Louisiana was providing an additional 500 school buses.

On the receiving end in Houston, though, the Astrodome looked at times like a squatters' camp in a war-torn country. The refugees from Louisiana, many dirty and hungry, wandered about aimlessly, checking bulletin boards for information about their relatives, queuing up for supplies and pay phones, mobbing Red Cross volunteers to obtain free T-shirts. Many found some conditions similar to those that they left behind at the Superdome, like clogged toilets and foul restrooms.

But in Houston, there were hot showers, crates of Bibles and stacks of pizzas, while in New Orleans, many refugees scrounged for diapers, water and basic survival.

The Senate convened a special session at 10 p.m. Thursday to pass the an emergency supplemental spending bill providing $10.5 billion for relief efforts.

Senator Thad Cochran, the Mississippi Republican who is chairman of the Appropriations Committee, said he had just returned from his home state. "The whole coastal area of the state has been destroyed, virtually destroyed," he said. "It was quiet. It was eerie. It was horrible to behold."

House leaders intended to hold a special session Friday to approve the measure.

Even as administration officials pledged vast resources to the region, however, Speaker J. Dennis Hastert, Republican of Illinois, told a local newspaper, The Daily Herald, that he was skeptical about using billions in federal money to rebuild New Orleans, given its vulnerability. "It doesn't make sense to me," Mr. Hastert said. "And it's a question that certainly we should ask."

He later sought to clarify his comments, saying in a statement: "I am not advocating that the city be abandoned or relocated. My comments about rebuilding the city were intended to reflect my sincere concern with how the city is rebuilt to ensure the future protection of its citizens."

Shea Penland, director of the Pontchartrain Institute for Environmental Studies at the University of New Orleans, had stayed in his Garden District home through the storm and its immediate aftermath. But on Thursday his generator was running out of fuel, and he was tiring.

"People have only so much staying power with no infrastructure," Dr. Penland said. "I am boarding up my house today and will hopefully be in Baton Rouge or the north shore tonight."

Annotazioni − Joseph B. Treaster reported from New Orleans, and Deborah Sontag from New York. Jeremy Alford contributed reporting from Baton Rouge, La.; Felicity Barringer from Metairie, La.; Christine Hauser from New York; and Simon Romero from Houston.