Patrice Evra, goalscorer Louis Saha, Kieran Richardson and Wes Brown were all targeted by the Portuguese club's supporters in the 1-0 win in Lisbon.

And a Manchester United source told Saturday's Sun newspaper: "All the players were upset and angry by the chanting."

United have written a letter of protest about the incidents to the Lisbon-based side and have called on UEFA, European football's governing body, to take action, the paper reported.

If found guilty Benfica could be hit with a heavy fine or ordered to play one or more games behind closed doors.

United's protest follows the call by gay rights campaigners to get Paul Scholes to apologise after he allegedly made a homophobic comment to the referee during the Group F clash. The 31-year-old former England international is alleged to have made the remark after receiving a yellow card from referee Frank De Bleeckere in the 10th minute of the game.

UEFA were waiting for reports from the match delegate and the referee before deciding whether to follow up the complaint.