Protesters are starting what they've said is an effort to shut down the nation's capital this weekend.
They're in Washington to protest the policies of the World Bank and International Monetary Fund, which are holding meetings.
Protesters chained themselves together, set tires on fire, and harassed police with false 911 calls.
DC police arrested more than 20 demonstrators who chained themselves together in a busy downtown intersection, jamming morning commuter traffic.
Fire trucks came out to put out tires set ablaze on the city's outskirts. Protesters also broke windows at a Citibank office and tossed smoky flares during a clash with police at another intersection, where more arrests were made.
They chanted, "This is not a police state."