Occupy Wall Street is continuing its six-month anniversary action today by trying to remain in Zuccotti Park overnight. Hundreds are in the park—around 600-700, according to Ryan Devreaux, who also photographed a tarp going up and protesters who "moved in." Of course, we know that the city doesn't act kindly towards tents in Zuccotti, since a judge ruled against them, but it's been up for 20 minutes so far. And here's what it sounds like in the park, via Jeff Smith:

The protesters are also practicing marching techniques: According to Animal New York's Bucky Turco, "Occupy protesters are doing training exercises. NYPD seem confused as they run, form walls, & then sit down." Plus, there's cake AND Michael Moore. Devreaux Tweeted right before 11 p.m.: "The tent in the middle of the park continues to fill with people planning to stay the night. Lots of energy here." Watch it live via TimCast:

Live stream by Ustream

Earlier today, a number of people were arrested during the daytime action. CityRoom's Colin Moynihan wrote:

Then the police began grabbing and arresting people, taking into custody at least half a dozen. Officers surged into the crowd, dragging protesters toward the street, as people yelled objections.

“They were grabbing people randomly,” Zachary Kamel said, adding that his girlfriend, Lauren DiGoia, had been arrested while dancing on the sidewalk.

One sergeant grabbed a woman wearing a green shirt by the bottom of her throat and shoved her head against the hood of a car. A moment later, another officer approached and forcefully pressed her head against the car before placing her into the back of a police truck.

Random arrests? That's... normal for the NYPD when it comes to OWS-related actions. Anyway, CityRoom's photograph shows a protester—who was allegedly asked if he was a terrorist—holding a sign that says "Bad Cop —> No Donut."

UPDATE: Apparently the cops just tore down a tarp and were unhappy when a posse of bagpipers joined the park. Via Jeff Smith, here's what the bagpipers (and apparently arrests/detainment) sound like (hint: turn the volume down):

A Great Big City.flickr.com/photos/agreatbigcity/6845547354/"> posted video of cops going into the park to take down the tent. Ryan Devreaux clarifies the tent-bagpiper sequence of events: "As everyone went to check out the police-on-bagpiper action, cops moved in and tore down the tent." Apparently the bagpipers are from France.

Now a second tent has been erected and there are "solidarity tents" in the air. Andrew Katz just Tweeted, "Mic check: Guy overheard NYPD planning to come in with a "wedge" formation" and Devreaux adds, "Police are mobilizing around Zuccotti's perimeter as a few hundred protesters stand their ground in the center." Brookfield Properties has asked the crowd to leave the park. And 1st Precinct Commanding Officer Edward Winski said the park is closed, that people will be arrested for trespassing.

Update 11:30 p.m.: Police entered Zuccotti and started tearing down the structures and, from what it looked like on the Livestream, pushing people down. Those in the park say it's "pandemonium" and "chaos" and protesters are "livid." But the cops are just enforcing "the rules"... that the NYCLU says are illegal. Dozens have been arrested/detained by police.

Devreaux just Tweeted, "Police are barricading the park. It's cleared. I witnessed countless violent arrests. No way to estimate numbers." Occupy Wall Street points out that setting up barricades on the "on the south side of #LibertySq" is "against court orders."

Some protesters are marching. Follow these people on the scene for more: Meg Robertson (@MegRobertson), NewYorkist (@NewYorkist), Andrew Katz (@katz), Ryan Devreaux (@rdevro), AnimalNewYork (@AnimalNewYork) A Great Big City (@agreatbigcity), Occupy Wall Street (@OccupyWallStNYC), Occupied WSJ (@OccupiedWSJ) and, for livestream, Tim Cast (@TimCast).