Multiple Occupy Wall Street marches have converged in Union Square for a rally and concert by Tom Morello, Das Racist, Dan Deacon, Immortal Technique and other performers. Here's live-streaming video:

Update 5:02 p.m.: And here's reporter James Thilman's visceral video of protesters marching defiantly down Fifth Avenue toward Union Square, as police struggle to get them off the street:

There are currently multiple reports of marijuana smoke filtering in, surprising no one. According to our wisecracking men on the scene, there are thousands of protesters in attendance.

Laurie Penny, who writes for The Independent and other outlets, offers a higher estimate of "around eight thousand, maybe more." Gothamist contributor Carrie Dennis says some parts of Union Square are packed, and police aren't letting people out of barricaded area. "Police wont let people out," she writes. One person inside pleaded with cops, "I Want to go home to my kids."

Update 6:05 p.m.: The march is struggling to begin, because the NYPD has barricaded protesters into Union Square, with very few exit points. Robbins estimates that at least 4,000 protesters are essentially stuck in the park, and only allowed to leave through tightly-controlled bottleneck exit points.

Update: 6:40 p.m.: Despite showing NYPD-issued credentials, police have repeatedly refused to allow Robbins to cross police lines. (He escaped Union Square through the subway system, and advises others to do likewise.) Broadway, he says, is essentially "a pedestrian plaza," and the demonstrators up front are slowing down in attempt to keep the march together.

Thilman reports that heavy traffic has ensued as a result of the march, and it seems a long night of marching and skirmishes await.