An FA Youth Cup tie between Liverpool and Manchester United at Anfield saw four red cards and several fans arrested amid ugly scenes.
During a 3-2 United victory, some of the away fans sang songs about the Heysel and Hillsborough tragedies of the 1980s that saw the deaths of 135 people. Three fans were arrested and six ejected from the ground.
A United spokesman said: "Singing songs about the Hillsborough and Heysel tragedies is disgraceful. We will deal harshly with anyone brought to our attention."
Former Liverpool striker John Aldridge, present during the Hillsborough disaster of 1989, said he was horrified by the behaviour of the fans on Sunday.
"I have never seen anything like that before at a youth game and I never want to see anything like it again," he told the Liverpool Echo. "It was disgusting.
"You get used to banter from United fans when they come to Anfield but to hear those songs about Heysel and Hillsborough was just horrible. The level of abuse was absolutely sickening.
"There was evidently a group who had just come to cause problems and I felt sorry for the families in the Manchester United end who just wanted to watch a game of football."
Two United fans were reported to have been spoken to after setting off flares. UEFA's disciplinary panel is already set to hear a case against travelling supporters said to have lit flares during United's recent Champions League game at Marseille.
The bad feeling in the stands eventually transferred to the pitch, with Conor Coady and Tyler Beckett dismissed for a late coming together of heads that left the Liverpool man bloodied.
Liverpool had taken a two-goal lead thanks to an Adam Morgan brace, but the game changed on a second-half penalty decision, which saw defender Stephen Sama sent off for a professional foul. United youngster Paul Pogba then followed when, after being booked for an unsporting run-up to the penalty, he continued to argue with the referee for a second caution.
Larnel Cole eventually despatched the retaken spot-kick, Ravel Morrison then equalised before adding the winner with a fine late volley.