Police moved in on Saturday to enforce a no-camping rule at sites occupied for months by protesters in Washington DC.br br The demonstrators weren't going without a fight.br br Officers in riot gear moved section by section through McPherson Square a few blocks from the White House.br br The National Park Service issued repeated warnings that it would start enforcing the no-camping ban.br br Police described the operation as 'nuisance abatement'.br br At least six people were arrested.br br The demonstrators have been camping in McPherson Square and Freedom Plaza in Washington in early October.br br They're protesting against the growing income gap, corporate greed and what they see as an unfair tax system that favours the rich.br br Some of the demonstrators are vowing to sleep on sidewalks or seek shelter in other places like churches.br br Sanitation workers under police guard moved in to clear the area of four months of accumulated debris from bedding to books and clothing.