Fighting between rival sets of Liverpool and Sevilla supporters broke out minutes before the start of the Europa League final on Wednesday.
The incidents, at St Jakob-Park, the home of FC Basel, occurred behind the Liverpool goal as the teams warmed up before the 1845 GMT final.
Stewards stepped in to try and break up the trouble, and minutes later dozens of riot police arrived to ward off further trouble.
The police, wearing protective helmets and wielding batons, lined themselves up on the stairwell behind the Liverpool goal in a bid to keep rivals sets of fans apart.
Sevilla are the two-time defending champions from 2014 and 2015 and they also won the competition in 2006 and 2007.
Liverpool, former three-time winners, are looking for their first European trophy since winning the Champions League in 2005.