CHICAGO (CBS) – NATO protesters, including Occupy Chicago members, briefly shut down the Michigan Avenue bridge and slowed traffic around the Loop in an impromptu march following a peaceful rally held by a nurse’s union at Daley Plaza this afternoon.

Dozens of the demonstrators marched through the Loop and gathered at Upper Wacker Drive and Michigan Avenue at the Chicago River, stalling traffic. Traffic on Michigan Avenue was closed, but some cars were getting by on Wacker.

LISTEN: WBBM Newsradio’s Mike Krauser reports

At least one arrest could be observed. Police assisted an officer who handcuffed a protester and led him away. CBS 2’s Kris Habermehl reported the protester had tried to hang a banner at the site, but succeeded only in tearing part of a NATO banner. That protester was charged with criminal trespass to property.

Police sources tell CBS 2 another person was arrested for battery to a lieutenant.

Police in riot helmets swarmed the area, and after about 15 minutes the marchers left and marched south through downtown streets.

Several marchers then sat down in the street at LaSalle and Jackson and blocked traffic for about 15 minutes. Later, the group marched down Jackson to Grant Park, where they were resting after several hours on the march.

LISTEN: WBBM Newsradio’s Bob Roberts reports

Friday evening, protesters had moved to the Congress Hotel to drum up support for ex-workers who had been displaced by non-union employees.

The earlier rally at Daley Plaza was without major incident and sponsored by the National Nurses United, in tandem with this weekend’s NATO summit at McCormick Place. At least one protester – dressed head to toe in black – was detained near the rally site and led away by police.

Police Supt. Garry McCarthy said the young man was not arrested, but was being held for questioning. A man identifying himself as the protester’s father decried the treatment.

“Having heard my son was arbitrarily pulled out of a crowd and detained does not make me proud to be an American,” the man told CBS 2’s Mike Puccinelli.

The protesters who clogged downtown streets had participated in the earlier rally, but did not appear to be affiliated with the nurse organization.

VIEW: Scenes From The Loop Protest

protest on jackson Impromptu Protest March Slows Traffic In Loop, 2 Arrested

Anti-NATO protesters march down Jackson on Friday. (Credit: Mason Johnson/CBS Chicago)

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