Police have moved to clear the Washington offshoot of Occupy Wall Street, arresting at least seven protesters on Saturday at the tent colony near the White House.

Stunned members of Occupy DC shouted angry slogans, but otherwise put up little resistance as National Park Service police swooped down on the scruffy four-month-old encampment in downtown McPherson Square.

By late Saturday afternoon only a few dozen of the original 100-odd tents remained, as police officers in riot gear and sanitation workers with forklifts and garbage trucks homed in on the Occupy DC library, information and medical tents.

Park Police spokesman David Schlosser told AFP four people had been arrested for "failure to obey a lawful order" after they locked arms and refused to leave the granite base of an equestrian statue in the heart of the park.

Lawyers for Occupy DC confirmed a further three arrests.

"If the US government enforced its banking laws like it did its park regulations, we wouldn't be in this damn park in the first place," Occupy DC activist Todd Fine said.

Occupy DC has been the last of the big encampments that popped up around the US in the wake of the Occupy Wall Street movement that took root in New York's financial district in September.

It moved into McPherson Square on October 1, bringing Occupy Wall Street's condemnation of inequality and corporate power to the centre of the K Street lobbying district, and growing in time to about 100 tents occupied by protesters.

Under pressure from Republican politicians and local businesses, the federal agency declared eight days ago that it would begin strict enforcement at both Occupy DC and a second, less controversial encampment nearby.