​Borussia Dortmund have released a statement explaining what happened between their fans and the supporters of Union Berlin, who clashed during their 3-1 defeat to the newly promoted side.

Union Berlin stunned Dortmund to pick up their first Bundesliga win, but the occasion was marred by violent clashes between the two sets of fans, with police being called to try separate the groups.

In an attempt to make things clearer, ​Dortmund took to their ​official website to give a play-by-play account of what actually transpired, adding that they will continue to investigate the incident and punish those responsible.

They said: "At the beginning of the match the Union fans put on a large choreographed display involving a huge banner which was hung over the roof of the home section. 

"A small number of Union fans had gone onto the stadium roof in order to display the banner, and, once the choreographed display was over, they moved away from the home section towards the part of the roof directly above the section for away fans.

Jadon Malik Sancho

"Approximately half an hour after kick-off, the Borussia Dortmund fan representatives were made aware of the fact that the only stairwell leading down from the roof was located in the area at the back of the section for away fans. 

"The Union fans on the roof were therefore planning to come down from the roof via the stairwell in question at some point during the first half. Certain BVB supporters had become aware of the presence of the Union fans on the roof - who had drawn attention to themselves through provocative behaviour - and tried to prevent them from coming down via the stairwell.

"At the same time, around 100 Union supporters in the home section got involved and attempted to force their way into the away section, many of them with their face covered. The security fences both outside and inside the stadium were enough to prevent this happening. 

Julian Brandt,Joshua Mees

"Nonetheless, in order to separate the two sides, the police deployed a large contingent of emergency personnel within the away section. Law enforcement officers resorted to the use of both pepper spray and batons. Many uninvolved BVB fans were injured or forced to leave the stadium early. Over 20 people required medical treatment.

"Borussia Dortmund unequivocally distances itself from all forms of violence and will continue to look into what happened on Saturday. We would like to wish all injured fans a speedy recovery."