Several Manchester United fans attacked Brentford supporters before the two sides met on Monday.
Video footage shows United fans rushing towards the Bees fans as they made their way towards the visitors' entrance at Old Trafford before kick-off.
Missiles were launched, punches thrown and flares set off in distasteful scenes amid an angry atmosphere, with widespread frustration at the deeply unpopular Glazer family that owns the club.
Riot police were forced to intervene to prevent the clashes between the fans spilling over into outright violence.
United supporters, seemingly the aggressors, sung loud songs, most notably about wanting part-owner Joel Glazer dead.
They chanted 'Gonna die, gonna die, Joel Glazer's gonna die' while piling towards the opposition fans, only prevented from clashing directly due to the ring of riot police and security staff.
The end of the video shows a long, linked line of police officers with masks and helmets on to protect themselves from smoke and potential attacks.
'Love United, hate Glazers' and 'United are the team for me' were also sung, with smoke from red and green flares billowing around, amid the anti-Glazer protests which have been ongoing for the last month or so.
Once again fans gathered outside the ground, chanting anti-Glazer songs.
Previous protests have involved fans boycotting the first 17 minutes of matches, one minute for each year the Glazers have been in charge at the club.
However on Monday, fans were urged to walk out on 73 minutes - 17 minutes before the 90-minute mark and the end of the game.
The campaign did not have a considerable effect, perhaps due to the success of the side on the pitch in their last home game of the season, although some fans were spotted departing.
On the pitch, things were happier for United, who turned in a committed and diligent performance out of sync with their recent showings.
Bruno Fernandes opened the scoring after nine minutes, with the bright Cristiano Ronaldo doubling the lead just after the hour mark with a penalty he won himself.
Raphael Varane scored his first goal for the club with a volley from a corner to cement the result late on.
Ralf Rangnick hit back at the doom-mongers hailing 'the fall of Manchester United' in his final programme notes as interim manager on Monday, as supporters staged a walkout at Old Trafford in protest against the Glazer ownership.
The German will now move into a two-year consultancy role at United, combining the job with becoming the new manager of Austria.
Rangnick has overseen the second half of a tumultuous season that could end with the club's lowest points tally in any Premier League campaign.
In his notes, Rangnick said: 'This season has clearly been a very difficult one for everyone at the club and from the short time I have been here, I can see how much everyone is hurting. I want to be clear... this is not the fall of Manchester United.
'This is a stumble along the way and when you stumble, you have to think quickly and clearly to regain your balance, so you can carry on moving forward. If we have clarity in our actions from now on, we can make big steps in the right direction.'
Erik ten Hag will leave Ajax this summer to replace Rangnick, becoming United's fifth permanent manager since Sir Alex Ferguson left nine years ago, immediately after their most recent league title win.