Updated

Police have arrested several anti-war protesters who rallied outside President Barack Obama's Chicago campaign headquarters in a prelude to much larger demonstrations expected during the upcoming NATO summit.

Protesters at the Monday demonstration organized by a group called Catholic Workers started by singing folk songs outside the Prudential Building in downtown Chicago.

Several protesters later entered the building's lobby to read a statement. Police arrested about a half-dozen activists who refused to leave after the statement was read.

The Catholic Worker group is launching what organizers call a "Week Without Capitalism" in protest of the next Sunday and Monday's NATO Summit. They're calling for more money to be spent on helping the poor and less on war.