UNITED NATIONS, Oct. 22 — An independent panel appointed to investigate the bombing of the United Nations headquarters in Baghdad in August said on Wednesday in a scathing report that security breaches, inadequate security analysis and poor management left the organization vulnerable to attack.

"The U.N. security management system failed in its mission to provide adequate security to U.N. staff in Iraq," said the authors, a seven-member committee named by Secretary General Kofi Annan and led by Martti Ahtisaari, a former president of Finland.

The panel said the organization had failed to assess thoroughly security in Iraq or respond to warnings, including intelligence reports that said the headquarters could be a target of an attack.

United Nations officials, the panel said, also dismissed offers of protection from the United States coalition in Baghdad.

Although the report acknowledged that improved security might not have prevented the bombing, which killed 22 staff members and visitors and injured more than 150 people, the investigators said the management and staff had failed to take steps that would at least have reduced the vulnerability of the mission and minimized casualties.

The panel, sounding an alarm throughout the United Nations network of missions, declared that the security system was "dysfunctional" and "provides little guarantee of security to U.N. staff in Iraq or other high-risk environments and needs to be reformed."

The 40-page report echoed in its severity the conclusions of the independent panels that Mr. Annan named to investigate the United Nations role in the massacres in Rwanda in 1994 and Srebrenica in 1995.

The attack, on Aug. 19, coupled with another outside the headquarters on Sept. 22, prompted Mr. Annan to pull out all but a skeletal foreign staff from Iraq and re-evaluate foreign missions of the United Nations.

"This report will cause immense pain and anger for those who lost family members and for those who survived the attacks, because it spells out that many of those who died did not have to," said Salim Lone, the communications director of the Baghdad mission, who added that it was characteristic of Mr. Annan's transparency that he commissioned the report.

Mr. Lone added that the mistakes in Baghdad "clearly went well beyond gross negligence."

Although the report did not directly criticize Mr. Annan, it disclosed that in spite of the highly volatile security problems before the bombing, including attacks on United Nations personnel and a car bombing against the Jordanian Embassy, the United Nations increased personnel in the Iraqi capital. Even after the United Nations bombing, the report said, Mr. Annan refused the recommendation of top advisers two times to withdraw the United Nations staff from Iraq, "primarily to maintain a core institutional presence."

"We were not pulled out even after the huge bomb," Mr. Lone said. "That's one thing that made no sense at all."

The panel did not fault specific people for the errors. Instead, it recommended a separate process to investigate the "breaches in the security system by the U.N. managers" and assign culpability.

Fred Eckhard, a spokesman for Mr. Annan, said in a statement: "The security of the staff has been the constant concern of the secretary general and the organization. The report will be closely studied, and steps taken to ensure early implementation of its main recommendations."

The investigators found that the United Nations did not adequately adjust to the worsening security in postwar Iraq and had an "ambivalent attitude" toward the threat, even as coalition forces were increasingly subjected to enemy attacks.

In the days before the Aug. 19 bombing, the investigators found, United Nations security officials received information about "an imminent bomb attack" near the headquarters. "It was also reported that other information was available around mid-July that the U.N. headquarters in Baghdad was under threat from a group loyal to the former regime," the report said.

A security report on Aug. 19 specifically referred to the danger of attacks by vehicles loaded with explosives.

Still, the panel reported, United Nations management "did not take adequate increased measures to protect its staff and premises."

The report also criticized the "ambiguous" day-to-day coordination between the mission and officials of the Coalition Provisional Authority, who had formal responsibility for the security of United Nations staff.

The report noted that United Nations personnel had asked the American-led coalition forces "on several occasions" to withdraw their security presence from around the headquarters, but failed to request alternative arrangements. Senior management, the panel said, "was uneasy with this highly visible military presence."

Among the defenses set up by the American military and removed at the United Nations' request, was a five-ton truck that blocked access to the service road that the bomber used to reach the headquarters. Later, the military laid concertina wire across the road, but United Nations officials requested that it be removed, too.

Mr. Annan's special representative in Iraq, Sergio Vieira de Mello, who died in the attack, ignored advice from two teams of United Nations security experts to move his office, which was close to the spot where the bomb, a truck filled with explosives, was detonated. Mr. de Mello, "declined and stated that he would leave the matter to his successor."

Mr. Ahtisaari's team enumerated many other problems, including violations of standard security protocol, as well as an overly cumbersome bureaucracy that slowed buying of security materials like shatterproof glass.

"The security awareness," the report said, "did not match the hostile environment."