Manchester United manager Jose Mourinho had water and milk thrown at him and Manchester City coach Mikel Arteta suffered a cut head during a post-match row.
United were upset at what they viewed as an excessive City reaction to Sunday’s 2-1 win at Old Trafford, which sent them 11 points clear at the top of the Premier League.
City’s players celebrated in front of their fans after the final whistle and coaching staff tried to persuade manager Pep Guardiola to join them, but he refused.
After the players headed down the tunnel, it is understood Mourinho made his feelings known outside the visitors’ dressing room as he made his way to post-match interviews.
The City camp reacted, with Brazil goalkeeper Ederson and Mourinho exchanging words angrily in Portuguese – but Mourinho carried out his post-match media engagements as normal and made no mention of it.
Arteta was left with a cut, though it is unclear how it was caused and sources from both clubs say no punches were thrown during the incident.