Updated at 6:27 p.m.
Demonstrators are now walking south on 14th Street NW and approaching New York Avenue NW, D.C. police said.
An alert said rolling closures will continue.
Original post at 6:13 p.m.
D.C. police are closing portions of K Street in Northwest Washington for demonstrators.
The demonstrators, who say they are marching for trade justice, plan to head to the Ronald Reagan Building and International Trade Center on Pennsylvania Avenue NW, authorities said. The march began at 4:30 p.m.
The group is walking westbound on K Street NW causing traffic disruptions, police said.
The evening delays followed a difficult morning commute on K Street when an hours-long barricade situation closed several streets.