PSG president Nasser Al-Khelaifi (C) and sporting director Leonardo (R) attend a training session with coach Mauricio Pochettino (AFP)
PSG threw away a two-goal advantage to lose 3-2 on aggregate at the Santiago Bernabeu, where a stunning second-half hat-trick from Karim Benzema sent the Qatari-owned club out in the last 16.
Sources have confirmed Al-Khelaifi and Leonardo marched downstairs from their box after the final whistle and that Leonardo was banging on the door of the referee's dressing room.
Their complaint is believed to have been around Benzema's first goal, when PSG goalkeeper Gianluigi Donnarumma was not awarded a free-kick, despite being pressured by the Real Madrid striker.
PSG coach Mauricio Pochettino said in his post-match press conference it was a "clear foul" and left the players feeling a "great sense of injustice".
According to Madrid newspaper Marca, Al-Khelaifi even stormed into the wrong room and was left confronting Real Madrid's match delegate Megia Davila. "He then had to be removed with difficulty and several people had to intervene," Marca added.
Tension between Real Madrid and PSG has been growing, with Madrid expected to sign their star striker Kylian Mbappe this summer. Mbappe has so far refused to extend his contract in Paris.
The clubs have also disagreed over the European Super League project, driven by Real Madrid president Florentino Perez but which PSG decided not to join last year.
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