German interior minister Hans-Peter Friedrich yesterday called for all professional clubs in the country to improve the behaviour of their fans, after crowd trouble marred a Bundesliga play-off.

“All 54 professional football clubs must agree on rules of conduct before the start of the new season,” Friedrich said in an article in the Koelner Stadt-Anzeiger, adding that fans must be told there was zero tolerance on violence.

“They must also tell them clearly that flares have no place in any stadium and in particular they must let it be known that there will be no favours for hooligans,” he added.

Friedrich’s comments come after a promotion-relegation play-off between top tier Hertha Berlin and second division Fortuna Duesseldorf on Tuesday was marred by a double pitch invasion that left players fearing for their lives.

The 2-2 draw saw Fortuna win 4-3 on aggregate and earn promotion to the Bundesliga at Hertha’s expense.

But the match in Duesseldorf was interrupted as fans fired flares onto the field and invaded the pitch deep into injury time, forcing the players to take refuge in the changing rooms for about 20 minutes and making them reluctant to return.

The German Football Federation (DFB) has launched an investigation and Hertha want a replay.

Friedrich said he was optimistic that new rules on fan conduct will be in place in time for the start of the new season on August 24.