(Updates with Los Angeles mayor's new conference)

By Dan Whitcomb

LOS ANGELES, May 4 (Reuters) - The mayor of Los Angeles cut short a trip to Mexico on Friday amid a furor over a May Day clash between police and pro-immigrant protesters, returning home to say what happened "was wrong" and he would set it right.

Mayor Antonio Villaraigosa, who was out of the country when police used rubber bullets and batons to clear protesters from a city park, ended his Latin American trade mission five days early and held a televised news conference at City Hall to address the outcry.

Villaraigosa told reporters he expected a thorough investigation into police activities in the park on Tuesday, but added: "We don't need a long and lengthy investigation to stand up and speak the truth. What happened on May 1 was wrong and I'm here to make it right."

The former Latino activist and crusader for immigrant rights who is considered a rising star in the Democratic Party, urged witnesses to come forward with their stories even if they were here illegally.

"You have my personal commitment that whatever your status in this country, you can come forward and tell your stories without fear," he said.

Los Angeles police have struggled for years to overcome a reputation for heavy-handed tactics that dates to the videotaped 1991 beating of black motorist Rodney King by four officers.

America's second most-populous city erupted into some of the worst urban riots in modern U.S. history a year later when the officers were acquitted in court. Two were later convicted in federal court and sentenced to prison terms.

At least four investigations have already been opened into the MacArthur Park incident, including two by the Los Angeles Police Department as well as probes by the FBI and the city's police commission.

Earlier on Friday, three residents who say they were caught up in the sweep filed federal lawsuits against the city.

Journalists were also caught up in the fray and Patricia Ballaz, a TV camerawoman who said she was injured when officers struck her with a baton filed a claim for damages. Ballaz said in the claim, typically a precursor to a lawsuit, that she suffered a wrist fracture, chest bruises and ankle injuries in the incident.

Some 25,000 people marched through Los Angeles on Tuesday as part of nationwide protests intended to demonstrate the political might of Latinos and help win amnesty for illegal immigrants. (Additional reporting by Tomas Sarmiento and Catherine Bremer in Mexico City)

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