Even before the growing crowds of Occupy Boston migrated from downtown's Dewey Park Square to the Rose Fitzgerald Kennedy Greenway early this morning, police began warning protesters to move back, or else. First they tweeted a message to @Occupy_Boston: "The BPD respects your right to protest peacefully. We ask for your ongoing cooperation." Then they went old-school, hand-distributing fliers that read, "If asked to leave an area, please do so peacefully."

But the group continued to swell to about 1,000, and the first riot police appeared at 1:20 a.m., followed by dozens of sheriff vans and paddy wagons. Eventually, more than 200 officers in riot gear surrounded the Greenway. Police Superintendent William Evans gave the crowd a two-minute grace period to disperse before arrests would be made. Ten minutes after that, police swarmed the park and cabled-tied roughly 100 protesters, the Globe reports, before carrying them off to jail.

Watch the clash unfold in the video above. [Boston Globe, Video via Occupy Boston]