Hundreds of the Dutch club's fans, many of whom had been drinking heavily in the Rome sunshine, hurled smoke bombs and other projectiles at a large contingent of police in the Piazza di Spagna, witnesses said.
The police reacted by charging them and clearing the square before shepherding the Dutch supporters onto buses bound for the city's Olympic Stadium, where Feyenoord was due to face Roma in a Europa League match on Thursday evening.
Rome mayor Ignazio Marino took to Twitter to voice his anger, describing the city as "devastated and injured."
Marino said he had been in touch with the Netherlands' ambassador. "This will not stop here," he said.
Roma devastata e ferita. In contatto con Prefetto, Questore e Ambasciatore d'Olanda. Non finisce qui #RomaFeyenoord— Ignazio Marino (@ignaziomarino) February 19, 2015
After the clash the square was left strewn with bottles, cans and other detritus. Many of the surrounding shops had pulled down their shutters and closed.