Rudolph W. Giuliani, the former Republican mayor of New York lionized for bringing together a city and nation after the Sept. 11, 2001, attacks, told the commission investigating the terrorist strikes Wednesday that emergency personnel did all they could in the face of catastrophe and that "the blame should clearly be directed at one source and one source alone: the terrorists who killed our loved ones."

Giuliani's testimony, delivered on the second day of this month's emotional and often tumultuous hearings, served as a rebuke to the panel and its staff, who on Tuesday reported that communication problems and turf battles had hampered the emergency response to the World Trade Center terrorist strikes.

The commission's staff expanded on that conclusion on Wednesday, issuing a new report suggesting that more people might have been saved from the burning South Tower of the trade center if fire officials had reacted differently. The panel also found that the emergency response to the crash of American Airlines Flight 77 into the Pentagon was "mainly a success" because of centralized command procedures.

Giuliani, who was loudly heckled on several occasions, urged the 10-member bipartisan commission to evaluate the events of that day with "compassion." He also testified that he had not been informed by federal officials or his aides about the surge in threats of terrorism detected by the federal government in the summer of 2001, including a now controversial intelligence document given to President Bush a month before the attacks. But he added that he did not believe the city could have been any more alert to a possible terrorist strike.

"We are all hurt," Giuliani said. "We're all very, very angry. And we're all feeling the loss of heroes that we love. . . . Our enemy is not each other, but terrorists who attacked us."

The commission, which has held most of its hearings in the staid corridors of Washington, has clearly rubbed nerves raw here in Manhattan by finding fault with the performance of firefighters, police officers and other rescue workers who rushed to the towers that day. Commission members sparred Tuesday with several New York officials, one of whom called such criticism "outrageous" and, to reporters gathered outside, "despicable."

The audience at New School University in Greenwich Village, which included hundreds of victims' relatives, was boisterous on both days of testimony, frequently erupting in applause or boos. During the most serious disruption on Wednesday, crowd members yelled "Lies!" and "Talk about the radios!" during Giuliani's testimony, referring to problems with fire department radio units. One spectator was forcibly removed as he shouted repeatedly, "Your government trained and funded al Qaeda!"

The commission members themselves were far more restrained on Wednesday, showering Giuliani with praise for his leadership and avoiding many of the barbed questions they had asked of others a day earlier. James R. Thompson, a former Republican governor of Illinois, appeared to acknowledge a retreat by saying that the panel would not be able to get support for reforms if it is seen as "second-guessing."

"We are not engaged in a search for villains," Thompson said. ". . . It would dishonor the memory of those who died on Sept. 11 if we don't learn the lessons."

After the close of the hearing Wednesday, Commission Chairman Thomas H. Kean and Co-Chairman Lee H. Hamilton released a statement expressing admiration for "the civilians, firefighters, police officers and emergency personnel, living and dead, who exhibited courage and determination under horrifying, overwhelming conditions. Their acts of heroism exceed our ability to praise."

However, one member, former Nebraska senator Bob Kerrey (D), president of the university that hosted the hearings, said he did not agree with Giuliani that "it's an either-or choice" between blaming terrorists and examining faults in the emergency response.

Giuliani outlined his own actions on the day of the attacks, recalling his shock at seeing a man jump from one of the twin towers. He testified that by "standing their ground" and attempting to rescue people, firefighters and others sent a message to terrorists that the United States was not weak.

Many victims' relatives complained later that the commission had gone too easy on Giuliani, contending that his performance after the attacks should not shield him from tough questioning. "He did a good job in many ways, but that was an hour and a half of congratulations," said Mindy Kleinberg, whose husband, Alan, died at the World Trade Center. "There are many questions that needed to be asked that were not asked."

New York Mayor Michael R. Bloomberg (R), who took office four months after the attacks, testified on Wednesday in defense of a new city emergency plan that has drawn criticism from outside experts and members of the commission. Bloomberg said that security measures taken since the attacks mean that "New York is the safest big city in the country."

Others testifying Wednesday included Homeland Security Secretary Tom Ridge, who defended the federal government's anti-terrorism efforts since the attacks, and Arlington County Fire Chief Edward P. Plaugher, who endorsed the type of centralized command system used in response to the attack on the Pentagon.

In a report issued before Wednesday's testimony, the panel's staff found that New York fire officials had failed to realize that they could have dispatched firefighters more quickly to the South Tower in the crucial minutes after the skyscraper was hit by the second plane.

Because of a lack of timely information, commanders dispatched new fire units to the South Tower instead of turning to units on hand in the North Tower. As a result, the additional firefighters arrived later and, in many cases, were killed in the ensuing collapse, the report said.

"The decision to handle the South Tower by dispatching new units meant that the number of firefighters available to help evacuees in that tower was relatively small for at least the first 20 minutes after the tower was hit, though that number sadly was rising in the minutes before that tower collapsed," the staff wrote in a 10-page report.

That haunting conclusion followed Tuesday's report, which acknowledged numerous acts of heroism and bravery on Sept. 11, 2001, but detailed widespread problems with the communication and organization of New York police and fire officials. The panel found that employees in the South Tower were erroneously told to stay there by 911 operators even after an evacuation order had been issued, and despite the fact that one of the stairwells in that tower remained passable.

By contrast, Wednesday's report praised the emergency response to the attack on the Pentagon in Northern Virginia, crediting a clear command system that vested a significant amount of power in one entity: the Arlington County Fire Department. But the commission report also cautioned that the "two experiences are not comparable" because of the scale of the calamity at the World Trade Center, which involved tens of thousands of potential victims and was far less contained than the devastation at the Pentagon.

But the staff also found that authorities in the Washington area reported communication glitches and other problems similar to those in New York. In an "after-action report" by Arlington County, for example, officials described problems with radio channels and equipment that had also plagued firefighters and police officers at the World Trade Center.

"Cellular telephones were of little value. . . . Radio channels were initially oversaturated. . . . Pagers seemed to be the most reliable means of notification when available and used, but most firefighters are not issued pagers," the Arlington report said, according to the commission.

The report concluded that command, control and communication problems "will likely recur in any emergency of similar scale." It recommended that New York adopt an "incident command" system to provide better coordination during major emergencies. Although Bloomberg and other New York officials testified that their new plan fits that definition, several commission members argued that the plan may cause more problems than it solves.

The commission also announced on Wednesday that it had selected W.W. Norton and Co. as the "authorized publisher" of its final report, to be completed by July 26. The paperback report will be distributed through booksellers for $10 per copy.

Lawyer Norman Siegel leads Christopher Brodeur out of the Sept. 11 commission's hearing after Brodeur interrupted former New York mayor Rudolph W. Giuliani, shown being sworn in at right. Giuliani told the panel: "Our enemy is not each other, but terrorists who attacked us."