Natalie Pike, a matchday presenter at the English club but in the Spanish capital as a fan, tweeted about a disturbance at a bar.
About an hour before kick-off she tweeted: "Just watched spanish police batter city fans. A big group of about 100 of us outside a bar opposite the stadium and they tore in battons up. No one doing any harm at all. Very scary stuff. So out of order."
She added: "Been going football 20 years never seen anything like it. On my life city fans doing nothing but singing and having fun.
"Women, kids, teenagers, all treated like scum. So out of order. Am so upset.
"The bar was so busy people were standing on the street outside. All innocent and friendly. No warning, no one asking us to move.
"The police just got there batons out and moved people along by smacking them."
City fans had travelled in large numbers for the eagerly-anticipated Group D opener.
Source: PA
Source: PA