Protesters, police clash at NATO summit (27 images)

Protest organizers at the NATO summit in Chicago said some protesters were injured in a clash with police late Sunday after a day of mostly peaceful protests. A Chicago city official, speaking off the record, told CNN protesters identified as aggressors were "extracted" after an estimated 50-75 protesters threw objects at police and refused to leave the area. A Chicago city official told CNN protesters identified as aggressors were "extracted" after an estimated 50-75 protesters threw objects at police and refused to leave the area. Approximately 20,000 protestors marched on NATO's biannual summit.

Police block LaSalle street to Occupy Chicago protestors as they march from the Boeing corporate headquarters to President Obama's campaign headquarters in downtown Chicago, May 21, 2012 during the 2012 NATO Summit. Protestors descended on the city of Chicago to rally during the 2-day biannual summit. UPI/Mark Cowan

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Occupy Chicago protestors demonstrate outside of the Boeing corporate headquarters in Chicago, May 21, 2012 during the 2012 NATO Summit. Protestors descended on the city of Chicago to rally during the 2-day biannual summit. UPI/Mark Cowan

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An Occupy Chicago protestor demonstrates outside of the Boeing corporate headquarters in Chicago, May 21, 2012 during the 2012 NATO Summit. Protestors descended on the city of Chicago to rally during the 2-day biannual summit. UPI/Mark Cowan

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Occupy Chicago protestors demonstrate outside of President Obama's re-election headquarters in downtown Chicago, May 21, 2012 during the 2012 NATO Summit. Protestors descended on the city of Chicago to rally for a variety of causes during the 2-day biannual summit. UPI/Mark Cowan

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