Berlin - Borussia Dortmund's CEO and president met their RB Leipzig counterparts on Thursday to apologise for last weekend's violent attacks by hooligans as police say they have started prosecuting the culprits.
Dortmund police have reportedly started criminal proceedings in 32 cases after violent attacks broke out before last Saturday's German league match when hooligans set upon Leipzig fans, including women and children.
During the attacks, four police officers and 10 visiting fans were injured, but the levels of hatred aimed at RB and their fans have shocked Germany's football community.
Around 60 banners, many bearing insulting slogans aimed at Leipzig, were displayed by Dortmund fans inside the stadium.
Dortmund captain Marcel Schmelzer condemned the violence in a video message to fans at their stadium before Wednesday's German Cup win over Hertha Berlin.
Now CEO Hans-Joachim Watzke and president Reinhard Rauball have apologised in person.
"They stressed that no sporting or emotional rivalry justified either the verbal slurs and banners personally attacking Leipzig club officials or the violence towards RB Leipzig fans," read a joint statement from the clubs.
"Rauball and Watzke assured RB executives that Borussia Dortmund began investigating the incidents and identifying culprits immediately after the game and have co-operated very closely with police.
"They will, of course, keep RB updated of any developments and will bring together those responsible for the safety of spectators in order to establish how the situation could have escalated as it did.
"Representatives from both clubs agree that the goal must be to find a solution which ensures the events of last Saturday are not repeated in the future."
Dortmund can expect to be heavily punished when the German Football Association complete their investigation.
Borussia are already on probation after fans rioted following their German Cup final defeat to Bayern Munich on penalties last May in Berlin and were fined €75,000.
RB Leipzig were founded in 2009 by energy drinks giants Red Bull and reached the Bundesliga for the first time this season, but are widely unpopular because of their perceived commercialisation of German football.
Watzke had been one of RB's most outspoken critics, having said Leipzig "play football to perform for cans of drink".
Germany's coach Joachim Loew led the voices condemning Watzke's comments, which the World Cup winner said escalated the situation in Dortmund.