Manchester City have been criticised over a video that appears to show players and staff joining in a song that celebrates Liverpool fans being "battered in the street".
The video is thought to have been captured on an aircraft as the club's travelling party returned from a 4-1 Premier League win at Brighton.
That victory saw the Blues beat Liverpool to the title by one point.
It is unclear which players and staff - if any - are joining in the singing.
The song - which City described in a statement as a "regular chant during the 2018-19 season" - recalls Liverpool's defeat in last year's Champions League final in Kiev.
It cites fans being "battered in the streets" and "crying in the stands" and includes a line on Liverpool forward Mohamed Salah being injured - but with the original culprit, Real Madrid's Sergio Ramos, changed to City defender Vincent Kompany.
However, many of the party only join in at the "Allez, Allez, Allez" chorus.
"It's honestly embarrassing that some Man City fans think it's OK for their players to sing about fans being beat up," one Liverpool fan tweeted, while many more responded saying the video was "classless", "unprofessional" or "naive".
City also said in their statement that "any suggestion that the lyrics relate to Sean Cox or the Hillsborough tragedy is entirely without foundation".
Sean Cox was left with brain injuries after being attacked before Liverpool played Roma at Anfield in the Champions League in April 2018.
Three Italian fans were jailed for their part in the attack.