European soccer's governing body has opened a disciplinary case against Porto after fans allegedly targeted racist abuse at Manchester City players during a Europa League match.

The Union of European Football Associations says Porto will face a charge of ''improper conduct of supporters'' at a March 29 meeting of its disciplinary panel.

City formally complained to UEFA after last Thursday's match in Portugal when Mario Balotelli and Yaya Toure, who are both black, reported hearing abusive chants.

Porto has suggested that the English club's players and officials misheard chants directed at City's Argentine forward, Sergio Aguero.

The charge was brought under UEFA statutes relating to discrimination.

UEFA is obliged to act against ''anyone who insults the human dignity of a person or group of persons by whatever means, including on grounds of color, race, religion or ethnic origin.''

If found guilty, Porto faces a punishment ranging from a one-match stadium closure to being banned from a UEFA competition, plus a minimum fine of 20,000 euros ($26,500).

City won the first leg of their second-round matchup 2-1. The return leg is to be played in Manchester on Wednesday.