Several Dortmund followers vented their frustration at their side's 4-1 defeat at Hoffenheim against the multi-millionaire owner of the Bundesliga newcomers Dietmar Hopp.

Dortmund general manager Watzke, who was sat just a few seats away from Hopp in their temporary home of Mannheim on Sunday, admitted he had felt very uncomfortable.

"What happened in Mannheim was embarrassing, shameful and unworthy," he said on the Westphalian club's website.

"We will do all we can to ensure people who no longer abide by the values of a BVB fan no longer damage BVB's reputation."

One fan held up a personally insulting banner against Hopp, whose millions have helped Hoffenheim from non-league obscurity into the Bundesliga recently.

He has already been identified and is likely to receive a ban from all stadia throughout Germany.