WASHINGTON (CNN) -- Capitol Hill Police have arrested nine anti-war protesters after hundreds of activists held small rallies and swamped congressional office buildings to meet with lawmakers.

Capitol Hill Police Sgt. Kimberly Schneider told CNN the arrests were for unlawful assembly at the Rayburn House Office Building. Protesters had gathered in a central, outdoor courtyard of the building, throwing white roses into a frozen pool.

Less than an hour later, a separate protest at the Hart Office Building brought no arrests but sparked reverberating chants between protesters and some supporting staff members.

"What do you want?" shouted an unidentified Capitol staffer, acting as a cheerleader. The crowd shouted back, "Peace!"

At least 200 people filled the large atrium of the Hart Senate Office Building, their chants echoing ahead of meetings in senators' offices.

"This is a great," beamed Medea Benjamin, co-founder of the anti-war group Code Pink. "We are really putting the pressure on this Congress."

Her group was unmistakable, dotting the crowd with hot pink sweaters and scarves. Protesters also unfurled handmade banners and set up a small display of children's' shoes to represent the loss of life in Iraq. While women easily outnumbered men, the protesters were otherwise was diverse, including teenagers from Florida and holocaust survivors in their 80s.