Manchester United and Liverpool could face Uefa action after fans lit flares and were involved in scuffles during the Europa League last-16 second leg at Old Trafford.
Radio 5 live’s Ian Dennis reported that punches were thrown while the police had to form a “human wall” to protect Liverpool fans in the United section.
Seats were also thrown by supporters.
Great Manchester Police said there had been three ‘football-related’ arrests including assault and affray.
The game ended 1-1 with Liverpool winning 3-1 on aggregate to progress to the quarter-finals.
Guidelines from Europe’s governing body state that host clubs are liable for order and security inside and around the stadium.
All clubs may be subject to disciplinary measures for “inappropriate behaviour on the part of their supporters” including “the throwing of objects”, “the lighting of fireworks or any other objects” and “any other lack of order or discipline observed inside or around the stadium”.
Before the match had kicked-off, police had to remove a banner on the M602 motorway in Salford designed to taunt Liverpool fans heading to Old Trafford.
United fans avoided punishment by Uefa after after some of their fans sang offensive Hillsborough disaster chants during the first leg at Anfield.