They are demanding a ceasefire in the war in Gaza. Protester's calls have intensified over the Israeli assault on Rafah.
An Israeli airstrike in Rafah has been blamed for the deaths of 45 Palestinians at a refugee camp over the weekend.
The protest march was recently near Dearborn and Wacker in the Loop.
Chopper 7 was over the scene as protesters appeared to fill city streets and block traffic.
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