More than 500,000 strong immigration rights advocates marched in downtown Los Angeles, demanding that US Congress abandon attempts to make helping illegal immigrants a crime and to build more walls along the border.

Thousands of demonstrators march through the streets of downtown Los Angeles to protest legislation that cracks down against illegal immigrants, March 25, 2006. Thousands of demonstrators in California protested moves to impose stricter US immigration laws on Saturday, while President George W. Bush urged wary Republicans to take up his guest-worker proposal. [Reuters]

The massive demonstration, one of half dozen around the nation in recent days, came as US President Bush prodded Republican congressional leaders to give some illegal immigrants a chance to work legally in the US under certain conditions.

Saturday's march in Los Angeles was the largest in a series of demonstrations across the country. Police Cmdr. Louis Gray Jr. said aerial helicopters estimated the crowd.

Many of the marchers wore white shirts to symbolize peace and also waved US flags. Some also carried the flags of Mexico and other countries, and even wore them as capes.

Elger Aloy, 26, of Riverside, a premed student, pushed a stroller with his 8-month-old son at Saturday's Los Angeles march.

"Everybody deserves the right to a better life," Aloy said of the legislation.

The US House of Representatives has passed legislation that would make it a felony to be in the US illegally, impose new penalties on employers who hire illegal immigrants and erect fences along one-third of the US-Mexican border. The Senate is to begin debating the proposals on Tuesday.

US President Bush on Saturday called for legislation that does not force America to choose between being a welcoming society and a lawful one.

"America is a nation of immigrants, and we're also a nation of laws," Bush said in his weekly radio address about the emotional immigration issue that has driven a wedge into his party.

Bush sides with business leaders who want legislation to let some immigrants stay in the country and work for a set period of time. Others, including Senate Majority Leader Bill Frist, say national security concerns should drive immigration reform.

"They say we are criminals. We are not criminals," said Salvador Hernandez, 43, of Los Angeles, a resident alien who came to the United States illegally from El Salvador 14 years ago and worked as truck driver, painter and day laborer.

Francisco Flores, 27, a wood flooring installer from Santa Clarita who is a former illegal immigrant, said, "We want to work legally, so we can pay our taxes and support the country, our country."

On Friday, thousands of people joined in rallies in cities including Los Angeles, Phoenix and Atlanta and staged school walkouts, marches and work stoppages.

The Los Angeles demonstration led to fights between black and Hispanic students at one high school, but the protests were largely peaceful, authorities said. More than 2,700 students from at least eight city high schools and middle schools poured out of classrooms to join the protest.

In one of the largest protests in city history, Phoenix police said 20,000 demonstrators marched Friday to the office of Sen. Jon Kyl, R-Ariz., co-sponsor of a bill to step up enforcement along the US-Mexico border and create a temporary guest-worker program that would require illegals to leave after five years.

Activists in Georgia said tens of thousands of workers did not show up at their jobs Friday to protest a bill passed by the state House that would deny state services to adults in the US illegally and impose a 5-percent surcharge on wire transfers from illegal immigrants.