Jose Mourinho reportedly had to intervene to stop racist chants from Roma fans allegedly calling Zlatan Ibrahimovic a 'gypsy'.
The Italian side's trip to AC Milan ended in a 3-1 defeat despite Tammy Abraham's 40th-minute strike, with Olivier Giroud, Junior Messias and Rafael Leao all on target for the hosts.
But a feisty Serie A fixture was marred by reports of racist chanting, allegedly aimed at Ibrahimovic, by the away fans.
According to broadcaster DAZN via SempreMilan, the incident occurred just as the 40-year-old was coming off the bench, and just a few minutes before he would set up Leao for Milan's decisive third goal of the night at the Stadio Meazza.
The report states that Roma boss Mourinho - who managed Ibrahimovic at Inter Milan between 2008 and 2009 - heard the racist remarks coming from away fans.
The former Chelsea, Manchester United and Tottenham boss is then consequently said to have called the travelling fans to stop the abuse, which they reportedly immediately did.
However, MilanNews via SempreMilan report the racist songs and insults were restarted and continued even when Ibrahimovic - who does not have Romani origins - and his team-mates were going through their warm down.
It is not the first time Roma's supporters have hurled abuse in the direction of the Sweden international, who replaced ex-Arsenal and Chelsea forward Giroud in the 77th minute.
The former Man United and PSG star was booked in October's reverse fixture after urging the Roma fans to sing their taunts of: 'Sei uno zingaro' (you are a gypsy) louder following his goal in Milan's 2-1 in the Italian capital.
Roma were consequently handed a one-year suspended ban for the infamous Curva Sud section of the Stadio Olimpico, with Milan midfielder Franck Kessie also receiving racist abuse.
'We have zero tolerance for any form of racism,' Roma said in a statement after that game.
'The club has been committed to combating racism and any form of discrimination for years.
'As an organization, we continue to do everything we can to change the behaviour of some fans in a positive way.'
Ibrahimovic - who returned to Milan in January 2020 and signed a one-year extension last year - has scored seven goals in 15 appearances across all competitions this term.