LOS ANGELES (Reuters) - Angered by Arizona’s crackdown on illegal immigrants, Hispanic protesters took to the streets on Saturday to denounce the new law and call on President Barack Obama to act urgently on immigration reform at May Day rallies across the United States.

Protesters gather to speak out against stricter immigration laws, such as one passed recently in Arizona, at a May Day rally in Lafayette Square Park near the White House in Washington, May 1, 2010. REUTERS/Jonathan Ernst

In a sea of American flags and banners painted with “We Are All Arizona” and “Overturn Arizona Apartheid,” tens of thousands of marchers, dressed in white, swarmed downtown Los Angeles.

In Washington, a U.S. congressman was among 34 people arrested in a protest outside the White House.

Dozens of protests were planned by immigration rights activists in U.S. cities, including in the Arizona capital, Phoenix, where the governor signed the toughest immigration law in the nation eight days ago.

Activists want a repeal of the law that seeks to drive illegal immigrants out of the U.S.-Mexico border state and they want Obama to fulfill his election promise to overhaul immigration laws. An estimated 10.8 million illegal immigrants live in the United States.

“What is happening in Arizona is making the community come out to the street,” said activist Omar Gomez in Los Angeles.

The Arizona law requires state and local police to determine people’s immigration status if there is “reasonable suspicion” they are in the United States illegally.

Supporters say it is needed to curb crime in the desert state, which is home to some 460,000 illegal immigrants and is a major corridor for drug and migrant smugglers from Mexico.

Critics say the law is unconstitutional and opens the door to racial profiling.

Polls show it has the backing of almost two-thirds of Arizona voters and majority support nationwide. The law has prompted legal challenges and hurled immigration back on the front burner of U.S. politics in this volatile election year.

‘NO PLACE FOR BIGOTRY’

“Laws that make suspects out of people for no other reason than the color of their skin have no place in our country,” Los Angeles Mayor Antonio Villaraigosa, a Mexican-American, told marchers packing into the city center.

“We must show that bigotry has no place in the United States of America,” added Villaraigosa, a Democrat who is one of the most powerful Hispanics in U.S. politics.

Kellie Morrell, a waitress at a New York City restaurant that she said employs several illegal immigrants, was among a few thousand activists who took to the streets of New York.

“They work really hard and they deserve to not have to live in fear of arrest or being thrown into prison, or even worse,” she said.

In Washington, Democratic Representative Luis Gutierrez from Obama’s home state of Illinois, was arrested with 34 others after they locked arms and sat in front of the White House fence, chanting Obama’s campaign slogan, “Yes we can” in Spanish. The congressman was later released, a spokesman said.

Hispanics are the largest minority in the United States and a powerful voting bloc.

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Organizers had expected turnout at rallies to be at the highest levels since 2006 and 2007, when hundreds of thousands of immigration rights supporters marched in U.S. cities

Police estimated 50,000 people attended the Los Angeles rally, but organizers pegged the number at 250,000. Crowds in most cities appeared to be smaller.

In Chicago, where activists turned out to protest the Arizona Diamondbacks baseball team at a game this week, tens of thousands of marchers turned out. In the Boston area, some 2,000 people marched in favor of legalizing undocumented migrants.

Anger at the law spilled over the border to Mexico on Saturday, where activists toting placards reading “Justice for Migrants,” gathered outside the U.S. Embassy in Mexico City.

OBAMA’S PROMISE

Arizona’s law instantly revived efforts by Democrats to enact immigration reform six months before congressional elections.

A framework set out by Senate Majority Leader Harry Reid was quickly endorsed by Obama on Thursday, but analysts see only a slim chance of it passing.

Frustration at Obama for not delivering on an election promise to overhaul immigration laws was evident in placards like “Where is your promise Obama?”, and some doubted they would vote for Democrats in November congressional elections.

“They feel worse than neglected, they feel attacked,” said Joseph Antoine, 21, who was among 2,000 marchers in Boston. “They’re not going to be rushing to support Democrats in November.”