More than a million immigrants in the United States have taken part in a day of nationwide action to protest against proposed immigration reform.
Mass rallies were staged across the US as immigrants boycotted work or school and avoided spending money as a way of showing their worth to the economy.
Called A Day Without Immigrants, the protest took place as Congress wrestles with reforming immigration laws.
About 11.5m illegal immigrants live in the US, many of them of Latino origin.
The protests were aimed at persuading Congress to abandon the tough measures in a bill passed last year by the US House of Representatives that includes provisions to criminalise illegal immigrants and bolster border security.
A bipartisan Senate bill, currently stalled, would provide illegal immigrants a path toward citizenship and a guest-worker programme long favoured by President George W Bush.
But there is some way to go before the competing bills are reconciled and a compromise reached. A number of US politicians say illegal migrants should be sent home.
Some commentators say the emerging immigrant movement - the force of which was evident at nationwide demonstrations last month - can be compared with the civil rights protests of the 1960s and 70s.
"Everyone's an immigrant here. The only real American is the Indian," Puerto Rican-born Rene Ochart, a doorman in a Manhattan hotel, said of the campaign.
Despite Monday being a normal working day in the US, many businesses were forced to close as workers in industries including agriculture, construction and leisure withheld their labour.
Goya Foods halted distribution for the day, while Tyson Foods, the world's largest meat producer, shut nine of its 15 plants.
The biggest demonstrations on Monday were seen in the US cities of Los Angeles and Chicago.
Some 400,000 people are estimated by police to have taken part in two marches in Los Angeles.
Many of the marchers wore white - a colour chosen by protest organisers as a sign of solidarity with the illegal immigrants, while others marched draped in US or Mexican flags.
In Chicago, police said 400,000 people marched through the streets and in New York, supporters formed human chains at 1216 (1616 GMT) to symbolise 16 December 2005 - the day the controversial immigration bill was passed in the House of Representatives.
US ILLEGAL IMMIGRANTS
About 11.5m illegal immigrants in the US
Four out of 10 have been in US five years or less
75% were born in Latin America
Most enter via southern US border
California, Texas and Florida host most illegal immigrants
Many work in agriculture, transport and construction
There were similar, smaller protests in Miami and several other cities across the US.
California's State Senate has approved what lawmakers called "the great American boycott of 2006", describing it as an attempt to educate Americans about "the tremendous contribution immigrants make on a daily basis to our society and economy".
Melanie Lugo, a marcher in Denver, Colorado, told the Associated Press news agency: "We are the backbone of what America is, legal or illegal, it doesn't matter."
As well as staying away from work and joining marches, some immigrants protested by working but buying nothing, while others joined church services, candlelit vigils and picnics.
It is not yet clear what effect Monday's protest action has had on the economy.
The Democratic governor of New Mexico, Bill Richardson, told the BBC he was concerned the demonstrations would distract from the real issue - "the need for comprehensive immigration reform".
"I would rather have those demonstrators go to each of the congressional offices... and explain to their representatives how important this issue is," he said.
White House spokesman Scott McClellan said the president was not "a fan of boycotts" and was keen to see the new immigration laws approved.
In Mexico, the home country of most undocumented workers in the US, thousands of people took to the streets to express support for the protests in America.
Some waved banners in the centre of Mexico City reading "Migrants are honest workers, not terrorists".
The marches coincided with the 1 May bank holiday, and many trade unionists also voiced solidarity with immigrants in the US.