Four Atlético Madrid fan groups have said they will take legal action against UEFA over Julián Álvarez's disallowed penalty in the club's Champions League round of 16 defeat to Real Madrid.
Álvarez's spot kick in the decisive shootout at the Metropolitano -- after the tie had ended 2-2 on aggregate -- was ruled out after a VAR review determined that the Argentina international had touched the ball with both feet, as Real triumphed 4-2 on penalties.
The fans commissioned an expert report which they say calls into question the video evidence released by UEFA in the aftermath of the game, which European football's governing body said demonstrated that Álvarez had touched the ball twice.
In a statement released on Friday, the groups -- Atlético's International Union of Fan Clubs as well as "Senado Atletico," "Los 50" and "Señales de Humo" -- said they had decided to "jointly commence legal proceedings against UEFA."
"It was agreed, as an initial measure, to create a working group made up of renowned, prestigious lawyers, who will be responsible for designing the appropriate legal strategy to file the relevant complaint as soon as possible," the statement said.
"We want to publicly thank fan groups, club members and fans for the support shown for the idea of defending the dignity and values which our club's history represents."
Real beat Atlético 2-1 in the first leg of the round-of-16 tie at the Bernabéu on March 4.
In the second leg, Conor Gallagher's first-minute goal levelled the contest at 2-2.
In the subsequent shootout, Álvarez's penalty -- which he initially appeared to have converted -- was ruled out by VAR, deeming the forward to have slipped and touched the ball with both feet as he shot.
Antonio Rüdiger then scored to win the shootout for Real, 4-2.
"Atlético Madrid consulted UEFA about the incident which led to Julián Álvarez's penalty being disallowed," UEFA said later in a statement. "Although it was minimal, the player made contact with the ball with his supporting foot before shooting, as the video shows.
"Under the current rules, VAR had to call the referee to indicate that the goal should be ruled out. UEFA will initiate conversations with FIFA and IFAB to determine if the rules should be revised in cases where the double touch is clearly accidental."
The Atlético fan groups have questioned the video released by UEFA in support of that statement, saying that it had been edited.
Atlético coach Diego Simeone reacted angrily to the decision to disallow the penalty, challenging journalists in his post-match news conference to "raise their hands" if they had seen the ball move, and later blaming UEFA for eliminating his team from the Champions League.