LOS ANGELES, US - THOUSANDS of immigrants and rights groups marched across the United States on Thursday, renewing calls for reform to help bring 12 million illegal workers out of the shadows.

Tens of thousands of marchers were expected to turn out in Los Angeles later on Thursday for one of the biggest demonstrations, one year after a similar protest erupted in violent clashes between police and protesters.

Immigrant rights activists hope the protests - which were taking place in more than a dozen other cities including New York, Washington, Chicago and Miami - will draw attention to the issue of immigration reform.

About 10,000 people of Hispanic and Asian origin gathered in downtown New York's Union Square before a march to the federal immigration office.

In Los Angeles, organisers hoped as many as 100,000 would take to the streets, sharply down on the vast crowd of around one million that turned out at similar protests in 2006.

Police said 4,500 people had begun to gather in the early afternoon, but organisers put the figure at around 10,000.

Jose Gutierrez, leader of the Latino Movement USA, one of the organising groups, said the protests would give voice to the millions of undocumented workers across the country.

'It is imperative to raise the voice of the more than 12 million undocumented people who work in this country,' Mr Gutierrez said. 'Every day families are being separated because of the raids.'

Another activist, William Torres of the March 25th Coalition, said undocumented workers deserved the right to stay in the country legally.

'Is it fair that we only exploit them for their cheap labor and deny them citizenship when they love this country?' Mr Torres said as crowds carrying American flags and placards began gathering in downtown Los Angeles.

Winning support
Protesters in Los Angeles have also won support from the city's chamber of commerce, with the body's vice president Samuel Garrison saying recent immigration raids were hurting the local economy.

'The raids are frightening workers. They are worrying employers,' Mr Garrison told the Los Angeles Times. 'I think it's going to cause a lot of businesses to think twice about coming to Los Angeles.'

Los Angeles police are determined to avoid a repeat of the violent scenes that erupted at last year's protests in the city, where police were accused of heavyhanded tactics against marchers and media.

'I feel absolutely, totally confident that ... we're going to have a good event. I believe very strongly in the fact that we have a very well organized command structure,' said LAPD Deputy Chief Michael Hillmann.

A coalition of rights groups are expected to hold separate rallies in Los Angeles from 4pm local time. -- AFP