Thousands of Bay Area residents joined forces Saturday in San Francisco to protest the passage of Arizona’s controversial immigration bill, SB 1070.

The protesters marched noisily but peaceably from Dolores Park to San Francisco Civic Center on the day known globally as International Workers Day.

The traditional May Day observance took on a more heated tone, however, when protesters clashed at Civic Center with members of the Golden Gate Minutemen and Norcal Tea Party, conservative groups that held a counter protest in support of strict immigration laws including Arizona’s immigration bill.

Police erected barricades to separate the opposing groups and to prevent the possibility of violence. Protesters were limited to waving banners, chanting slogans, sounding bullhorns and waving fingers at each other from across the street.

“I am here to support my people, people who have no voice, or are too scared to fight for their rights,” said Richmond resident Esmeralda Frias, age 24.

“I am here in solidarity with people who are like me,” said San Francisco resident Elyse Gay, 52. “Like our forefathers, we all immigrated from somewhere.”

“Kill SB 1070,” added Vernal Primus, 58. “Start reforming immigration laws. That is why I am here today.”

But not all in attendance at the Civic Center rally were sympathetic to the SB 1070 protest.

“I am here to protest the illegal march,” said Alameda resident Elizabeth Kelly, age 66. “I am totally against amnesty for illegals. I am a legal immigrant who raised four sons who serve their country. What I witness are these countries’ illegals draining our system of our money and draining our system of resources.”

Steve Kemp, an activist in support of SB 1070, stated, “I am here to stand up for the 200-million Americans who believe that illegal immigration is wrong and wants it to stop.”

“We want the law to be followed in terms of immigration,” said Pleasanton resident Mark Vorgele, 56. “If your not here legally we’re not paying for you.”

SB 1070, signed into law by Arizona Governor Jan Brewer, seeks to “discourage and deter the unlawful entry and presence of aliens and economic activity by persons unlawfully present in the United States,” and provides law enforcement increased powers, “where reasonable suspicion exists,” to identify and deport undocumented persons.

The law’s passage has prompted condemnation and boycotts.

Constitutional law groups including the ACLU are preparing legal challenges to the new law on the grounds that it violates constitutionally protected civil rights and that it may lead to racial profiling and enforcement abuses.

Attorney General Eric Holder told reporters the Justice Department and Homeland Security Department are conducting a review of the state law which could result in a court challenge