SPEER AND ARAPAHOE -- Police and observers are estimating more than 3,000 people joined an antiwar group of Iraq veterans in marching from the Denver Coliseum through downtown.

The massive protest, whose numbers appear to remain above 2,000, has turned onto Arapahoe Street on its way to the Pepsi Center, escorted by hundreds of police.

Observers turned out in droves to watch the protest as it crept through downtown -- parents bringing children, workers on their way home and residents peeking out windows.

"They wanted to see what was going on," said Betsy Crane, a Denver mother of three who brought her children --ages 9, 7 and 5 -- to watch the protest. "They're interested in seeing police officers, as well as protesters."

The march is cosponsored by Iraq Veterans Against the War and Tent State University, starting at the coliseum with a free concert by rap-metal band Rage Against the Machine. The numbers have seemed to surprise even the protesters, some of whom expressed surprise when told of the estimates thus far.

About 50 Iraq war veterans lead the parade, which has stopped several times to allow the massive line of people to regroup into one section. At least twice, soldiers have read from a letter they sent to Democratic nominee Barack Obama, urging him to bring troops home from Iraq upon election as president.