Pro-immigration advocates in front of the Capitol in Washington, DC,01 May 2008

Thousands of demonstrators gathered in cities across the United States for annual May Day pro-immigration rallies Thursday, though turnout was significantly lower than in recent years.

Organizers say fewer people are taking part because the pro-immigration focus has shifted to civic participation and because of widespread fear of government raids against illegal immigrants.

People marched in cities across the U.S. including New York, Chicago, Milwaukee and Los Angeles

In Los Angeles, as many as 100,000 were expected - far fewer than the estimated one million people who took part in the event in 2006.

Organizers want immigration reform to be a major election year issue. Both Democratic presidential contenders - Senators Barack Obama and Hillary Clinton - supported a 2006 immigration reform proposal sponsored by Republican candidate, Senator John McCain.

That bill would have - among other things - offered conditional legal status to illegal aliens.

There are an estimated 12 million illegal immigrants in the United States.

Some information for this report was provided by AFP and AP.