"UEFA has opened disciplinary proceedings against FC Barcelona midfielder Sergio Busquets, who is alleged to have violated ... the UEFA Disciplinary Regulations by directing racist abuse towards a Real Madrid player," European football's governing body said in a statement on Thursday.

"The proceedings have been launched on the basis of evidence provided by Real Madrid (video and statement of club and player)."

UEFA said the alleged offence happened during the first leg of the tie at the Bernabeu on April 27. The other player was not named but is widely reported to be Real's Brazilian left-back, Marcelo.

The UEFA Control and Disciplinary Body will deal with the case on May 15, with the decision being communicated to the club the following day.

Barcelona won the away leg 2-0 before qualifying 3-1 on aggregate to reach the Champions League final on May 28 against Manchester United at Wembley.

UEFA handed down a three-match ban on Real coach Jose Mourinho after he made allegations of favouritism towards Barcelona, while Real defender Pepe was sent off in the first leg.

Barcelona reserve goalkeeper Jose Pinto, red-carded in a half-time melee in the first leg, received a three-match ban.

Real Madrid had asked UEFA last week to reconsider their decision not to investigate provocation by Barcelona's players.

UEFA has vowed to crack down on racism in football.