Three Leeds supporters, two police officers and two security staff needed hospital treatment as last night’s match in the Austrian town of Eugendorf descended into chaos.
The local constabulary were forced to deploy riot police during trouble in Salzburg and Eugendorf prior to kick-off and fighting between rival fans at full-time.
A group of around 100 Eintracht supporters confronted United fans after the crowd spilled onto the pitch at the end of the game.
Supporters from both clubs were arrested, including 17 from Frankfurt during those clashes.
Salzburg police said pepper spray was needed to control Eintracht’s following in Eugendorf town centre after the game, which Leeds lost 2-1.
A police statement read: “At the square in front of the stadium, runaway Leeds fans were again attacked by the Frankfurt fans.
“Eventually the situation moved to the centre of Eugendorf where action was taken to stop the attacks, among other things a pepper-spray operation by the police.”
Earlier in the day, police said “substantial problems” had developed when a bus carrying Frankfurt fans from Salzburg to Eugendorf was blocked after they refused to pay the fare.
Around 50 Eintracht supporters then “arrived on foot at the stadium and stormed the entrance”, leaving two security staff hurt. Two police officers were also injured and a Leeds fan was attended to by paramedics in the car park after full-time, suffering from facial wounds.
Salzburg police have not said how serious any of the injuries are.
Supporter Neil Slinn, 53, was caught up in the violence and suffered minor injuries.
He said: “A few of us went over to applaud the Frankfurt fans. I was going to shake their hands. Then their ultras jumped over the (advertising) boards and started attacking us. Some were wearing balaclavas and we were outnumbered.”
The police investigation is continuing and details of the offences have been passed to the prosecutor in Salzburg.