The clashes began when a group of 100 Schalke fans overturned trash cans, lit firecrackers and confronted a large group of BVB supporters.
The police could not prevent a mass brawl at the last second, as the two groups were cornered. Many fans were muffled due to their extremely aggressive behaviour.
Peaceful fans ran away in panic, with police horses galloping into the crowd and large amounts of pepper spray being dispensed by officers.
Half an hour before the game got underway huge clashes erupted between rioters. Police officers were attacked and a water cannon was used to deter Schalke perpetrators."There were fights and vandalism around the stadium," a police spokeswoman told DAPD. "The officers were able to get the situation under control, but only with the massive use of pepper spray, horses and dogs.
"Also water cannons were needed. There were several minor injuries and 100 rioters came into police custody.
Another police spokesman added: "The whole city is under siege. Today it's bad, in recent years there were far fewer riots. We fear that it will continue after the game."
Around 1,000 officers were on duty - four times the usual number for a typical matchday.