Two Dutch Ajax supporters have been stabbed in Milan during a spat ahead of the Champions League game with AC Milan, according to local reports.
The injured - one in serious conditions - have been taken to the nearby San Carlo hospital.
Earlier, a group of 300 drunken Ajax fans attempted to break into the Milan Point in central San Fedele square but were forced back by riot police. Other fans confronted authorities in front of hospital Fatebenefratelli in Principessa Clotilde square.
Groups of drunken Ajax supporters raided Milan city centre throwing objects and shouting insults to locals.
The incident came after Dutch supporters clashed with protesters from Italy's Pitchfork movement.
Violence erupted in Milan when 20 Ajax fans got off their bus and hurled beer cans and insults at the demonstrators in the central Loreto Square.
Police intervened quickly to break up the fighting. There were no reports of injuries.
The Pitchfork movement, which started with a loose group of Sicilian farmers concerned about rising taxes and cuts to agricultural state funds, has evolved into a nationwide umbrella grouping of truckers, small businessman, the unemployed, low-paid workers, rightwing extremists and ultras football supporters.