LOS ANGELES, May 3 — Chief William J. Bratton of the Los Angeles Police Department said Thursday that the episode here in which police officers clashed with demonstrators and journalists on Tuesday at an immigration rally was the “worst incident of this type I have ever encountered in 37 years” in law enforcement.
Eight officers and at least 15 civilians were hurt, the police said, with people still calling the department on Thursday to report injuries. Mr. Bratton said 240 nonlethal projectiles were fired by the police into the crowd.
“Clearly, something went wrong here,” he said in a interview.
After a request by Mr. Bratton, the F.B.I. announced Thursday that it would open a civil rights inquiry into the incident, which has drawn outrage from immigrant and civic groups and journalists’ organizations and a rebuke from the City Council. On Wednesday Mr. Bratton announced two internal investigations by the Police Department.
News video images of the incident that erupted at a peaceful gathering in MacArthur Park, west of downtown, showed the police marching into the crowd, shoving and knocking down demonstrators and journalists with batons and firing rubber bullets at close range.
In television and press interviews throughout the day, Mr. Bratton said he was troubled by the police action he saw on the videos, and he sought to assure the city that he intended full disclosure of the facts.
Organizers of the May Day rally, whose theme was a call for broad changes to immigration laws, said they had held extensive negotiations with the police in preparing for the demonstration. They said the police did not follow the agreed-upon procedure in case of a disturbance.
“It completely broke down,” said Victor Narro of the National Lawyers Guild, who was the organizers’ liaison with the police.
Bob Baker, president of the Los Angeles Police Protective League, appealed in a statement for “no rush to judgment.” He said the clash had started after the demonstrators threw rocks and bottles. “Our officers gave a legal dispersal order and were met with violence,” Mr. Baker said. “In the coming days it will become clear what transpired.”
According to demonstrators, organizers and journalists who witnessed the incident, a band of youths who were not affiliated with organizations formally participating in the rally confronted the police at least one block from the park. The youths, some covering their faces with bandanas, taunted the officers and by some accounts threw rocks and bottles at them.
Police officers in riot gear lined up in rows and pushed the youths back down the street into the park, the witnesses said. “They started moving in,” said Angela Sanbrano, executive director of the Central American Resource Center, an event organizer. “They started beating up on anybody that didn’t move.”
The police said they declared the assembly unlawful and issued orders to clear the park. But many demonstrators said they did not hear the orders, and others, who spoke only Spanish, did not understand them.
Nine people were arrested for various offenses, including assault with a deadly weapon for throwing rocks at officers, the police said Wednesday.
For the past two days, local television viewers have seen video of Christina Gonzalez, a reporter for the Fox News affiliate, KTTV Channel 11, being repeatedly shoved by an officer with a baton. When Ms. Gonzalez knelt to help a camerawoman, Patti Ballaz, whom the police had pushed to the ground, an officer angrily threatened Ms. Gonzalez with arrest and then grabbed her shoulders, spinning her abruptly to the side.
“You can’t do that!” Ms. Gonzalez cried out. “You know that!”
Ms. Ballaz suffered a hairline fracture of a wrist.
Another reporter, Patricia Nazario from KPCC-FM, a National Public Radio affiliate here, said she was talking to her editor on her cellphone when an officer struck her in the back with a baton.
Ms. Nazario said she faced the officer and told him she was a reporter. He struck her again with the baton on her left thigh, she said.
“It happened so fast and I was on the ground,” she said. “It was like they were robots, on autopilot.”
After examining videos of the events, Marc Cooper, associate director of the University of Southern California Annenberg Institute for Justice and Journalism, said, “It seems to be a prima facie violation” of policies the police worked out with the American Civil Liberties Union in 2002 in the wake of scuffles with the press at the Democratic National Convention in Los Angeles in 2000.
The incident occurred as Mr. Bratton seeks to become the first police chief to earn a second five-year term since the city imposed term limits on high-ranking police officials in 1992. Although he has reduced the city’s crime rate by roughly 25 percent, his department has been dogged by the widely held perception that officers are often needlessly forceful.
The 1991 beating of Rodney G. King by the police and the acquittal a year later of the officers charged with using excessive force prompted riots; in the 1999 Rampart scandal, an antigang unit was accused of framing people, robbing suspects and other brutal conduct.