WASHINGTON, D.C.  — Capitol police swooped in on protesters unfurling banners at a U.S. Senate office building in Washington on Tuesday as part of the Occupy DC movement, arresting at least six, NBC reported.

Demonstrators stormed the Hart building's atrium and dropped large banners, one which said "End War Now," the other "People for the People." As soon as they displayed their signs, Capitol police arrested them, NBCWashington.com said. Dozens of others ran through the building — which holds the offices of Democratic Sens. Dianne Feinstein and Harry Reid as well as Republican Marco Rubio — with smaller signs, according to NBC.

The arrests in Washington come during the second week of Occupy DC demonstrations, part of a movement that began in New York last month to protest against perceived Wall Street excesses and other social issues and has spread to cities across the nation. Tuesday's Washington arrests followed a rash of police activity in an Occupy Boston event overnight, in which about 100 protesters were arrested after they refused to leave a park in the city, police reportedly said.

Tensions boiled over early on Tuesday in downtown Boston, where police arrested more than 100 protesters after the Occupy Boston group expanded its footprint and was told by authorities to move back.

Riot police arrived near the Rose Fitzgerald Kennedy Greenway park at about 1:20 a.m. ET with dozens of sheriff vans and police wagons arriving minutes later, The Boston Globe reported.

More than 200 officers surrounded the Greenway and Police Superintendent William Evans gave the protesters two minutes to leave or be thrown in jail, according to the newspaper.

‘"The people united will never be defeated," "this is a peaceful protest," "the whole world is watching," the crowd chanted, according to the Globe.

The paper said officers went into the park about 10 minutes later with another warning given over loudspeaker. Protesters were then made to lie down, cable-tied and taken away. Tents were torn down.

Boston Police Commissioner Edward Davis told the Globe that no one sustained any injuries, although an officer was hit in the face.

The paper said many of the protesters — about 1,000 people had gathered there earlier — left the park.

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It added that some in the crowd shouted at police "you don’t have to do this" and "who do you protect, who do you serve?"

Matthew J. Lee  /  Boston Globe

Boston police moved in and began arresting scores of Occupy Boston protesters who refused to leave early Tuesday morning.

Jamie Kenneally, a police spokesman, told The Washington Post that the arrests were mainly for trespassing.

"Now they've moved to another part of the Greenway and that's not acceptable," commissioner Davis told NBC-affiliate WHDH earlier.

A conservancy group had planted shrubs worth around $150,000 along the greenway and officials were worried about damage, The Washington Post reported.

'No use for police'
John Nilles, 74, who served in Vietnam and is a member of Veterans for Peace, told the Globe that he was knocked to the ground during the arrest operation, banging his knee.

"I have absolutely no use for police anymore. I don't know what I'm going to do," he told the paper.

Another protester, Shawdeen Vatan, 21, of Arlington, Mass., said she was not surprised at what happened.

"We're being seen as a legitimate organization," she said. "People are panicking and trying to get us out of here."

Occupy Boston used social media to alert supporters as officers arrived and called for more people to come.

"SWAT TEAM putting on RIOT GEAR on High St. PLEASE JOIN US NOW!," it said on its Facebook page.

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Tension had been building late Monday night after Occupy Boston members expanded their footprint in downtown Boston.

"The BPD respects your right to protest peacefully. We ask for your ongoing cooperation," the Boston Police Department said in a tweet to @Occupy_Boston, but did not mention any ultimatum.

Protesters' tents have been in Dewey Square Park in downtown Boston all month, but on Monday they expanded to a larger section of the nearby Rose Fitzgerald Kennedy Greenway.

Many linked arms Monday evening in a show of solidarity on their expanded turf.

In fliers handed out on site in Boston, and in a press release, the police told protesters: "If asked to leave an area, please do so peacefully."

Police said officers would arrest those knowingly in violation of the law "if necessary." They also warned protesters they would use video cameras to record any disorderly behavior.