Premier League club Manchester City has filed a complaint against FC Porto alleging supporters of the Portuguese club chanted racial slurs at City players during the Europa League clash at the Estadio Dragao last Thursday.
City, who won the match 2-1, filed a formal written complaint against Porto, on the grounds of "improper conduct of supporters" after Mario Balotelli and Yaya Toure (both of African desent) allegedly heard the home crowd chant racially abusive slurs against them.
According to Uefa disciplinary regulations, Porto, who will be called before football bosses on 29 March, could be hit with a €20,000 (£16,700) fine and other penalties. That could include playing matches behind closed doors, a stadium closure, a match forfeit, the deduction of points or disqualification from the competition.
However, Porto officials claim City's players and officials misinterpreted the chants. Their position is that the chants were actually meant for City's Argentinean striker Sergio Aguero.
Two prominent England footballers - Liverpool's Luis Suarez and Chelsea's John Terry - have both come under severe criticism for racially abusing Manchester United's Patrice Evra and Queens Park Rangers' Anton Ferdinand, respectively.