To mark the six-month anniversary of Occupy Wall Street, hundreds of OWS protesters took to lower Manhattan and Zuccotti Park to march today—and it seems there's already been several skirmishes with police. According to Allison Kilkenny, at least four demonstrators have been detained (and possibly arrested) by police; in addition, at least one cop has been injured and taken to New York Downtown Hospital. You can watch the livestream of the protest (which may be going in and out) below.

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Reporter Andrew Katz says there have possibly been six arrests now; he described the atmosphere at Zuccotti: "Haven't seem Zuccotti like this in months. Some instigation by protestors but police seem tense today, too." Guardian journalist Ryan Devereaux adds, "Sounds like there were btwn 4-6 arrests on sidewalk. Witness says he saw one arrestee punched in the head 10-15 times while subdued." Katz was also witness to a protester interacting with Detective Rick Lee, aka Hipster Cop: "I respect your style but you're still a cop."

Check out video of people being arrested below:

Kilkenny tweeted that protesters were pointing to two officers who they blamed for starting the altercation: "Protester alleges this all started because officer Winski grabbed him and officer Murray shoved him." They are referring to 1st Precinct Commanding Officer Edward Winski, who has had several run-ins with OWS protesters; last September, he reached over police barricades to detain an OWS protester during a march, and in December arrested protester Justin Wedes as he was passively filming the police.