Police in riot gear clamped down on the Washington offshoot of Occupy Wall Street on Saturday, seizing tents and bedding from the four-month-old tent colony and arresting seven protesters.

Stunned members of Occupy DC in McPherson Square, three blocks from the White House, shouted words of anger, but otherwise put up no resistance as the National Park Service swooped down at dawn on the scruffy encampment.

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

Lawyers for Occupy DC confirmed a further three arrests, including one protester seen by AFP being hustled away after reading aloud a few sentences about free speech from a book by late US historian and activist Howard Zinn.

Protesters initially agreed to pull down a huge blue tarp they called a Tent of Dreams that they had defiantly draped over the statue of Civil War general James McPherson on Monday.

But they looked on in dismay as police -- some in yellow or white overalls, others with riot shields and helmets -- started taking away entire tents, despite expectations that only sleeping gear would be seized.

"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, 31, told AFP as he watched the clearout.

Occupy DC has been the last of the big encampments that popped up around the United States 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 epicenter of the K Street lobbying district, and growing in time to around 100 tents.

But while other encampments faced evictions, Occupy DC endured in part due to the National Park Service's willingness to bend its own no-camping rules and classify the protest as "a 24-hour vigil."

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

Dozens of police, some on horseback, and with a helicopter overhead, converged on McPherson Square at dawn. Surrounding streets were closed off and barricades went up around the park. News media were permitted on the scene.

At one point, a cherry picker was brought in to remove a Guy Fawkes mask that occupiers had mischievously placed on the face of general McPherson when the Tent of Dreams was erected.

"We are not here to evict," but to verify compliance with the no-camping rules, one police officer told protesters. Those rules define camping as the use of park land for "sleeping activities."

"The tents are not a problem. The tents are fine as long as they are symbolic," Schlosser told AFP.

But by mid-morning, as police swept the southeast corner of the park, it was apparent that any tent with bedding inside would be confiscated -- sending occupiers elsewhere in the park scrambling to pack up their belongings.

"I guess they're trying to keep us on our toes, or off our toes," said Virmeko Scott, 30, after he stashed his sleeping gear, but not his tent, in a clear plastic bag for storage in a nearby Lutheran church that offered to take care of occupiers' gear.

Scott was confident the clampdown would not be the end of Occupy DC. "There's going to be more tents down here," he told AFP. "They're going to multiply."

Another occupier, Melissa Byrne, said the camping ban amounted to an order to quit the site altogether. "We have been evicted," she said, "but word is going to get out and we're going to be back stronger than ever."