US President Barack Obama said Wednesday that he was "deeply disturbed" by video footage which showed a white Chicago police officer shooting dead a black teenager.

"Like many Americans, I was deeply disturbed by the footage of the fatal shooting of 17-year-old Laquan McDonald," Obama wrote on his official Facebook page.

"This Thanksgiving, I ask everybody to keep those who've suffered tragic loss in our thoughts and prayers, and to be thankful for the overwhelming majority of men and women in uniform who protect our communities with honor."