VOLGOGRAD, Russia -- Both FIFA and sources close to World Cup referee Mark Geiger have denied accusations from Morocco's Nordin Amrabat that the American official asked for a Portugal player's shirt during the game he worked on Wednesday.

Morocco complained about Geiger's performance after losing to Portugal 1-0 in the match, which was his first on-field assignment at the 2018 event, and midfielder Amrabat raised the prospect of impartial behaviour by the referee in an interview with Dutch broadcaster NOS.

"I don't know what [Geiger] is used to, but he was very impressed by Cristiano [Ronaldo]," Amrabat said. "I've been just told by Pepe that in the [first half], he asked if he could have his shirt. Come on, man. What are we talking about? ... We are at the World Cup, not a circus here."

FIFA condemned the allegations and said in a statement that Geiger has refuted the claim from Amrabat, who controversially played in the game despite suffering a concussion against Iran last week.

"FIFA referees are under clear instructions with regard to their behaviour and relationship with the teams at the 2018 FIFA World Cup Russia and it can be confirmed that Mr. Geiger has acted in an exemplary and professional manner as an appointed match official," the statement said.

FIFA statement related to media reports about FIFA Referee Mark Geiger @FIFAWorldCup pic.twitter.com/SZ6QHMfyPq — FIFA Media (@fifamedia) June 21, 2018

Sources close to Geiger also denied to ESPN FC that he made such a request.

"It's laughable, these allegations," said one source, who asked to remain anonymous because he is not authorised to comment on refereeing issues at the World Cup. "We saw it on Twitter last night and laughed at the ridiculousness of it."

With the implementation of video assistant referee (VAR) technology throughout the event, all communication between the referee, his assistants and those in the VAR booth are recorded. The recordings are later used for training and to provide feedback on a referee's performance.

If Geiger said what is alleged, the source said, "the audio would be recorded and it would be on tape. It's a live [microphone] at all times and there is no way for Mark to mute it."

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There was some confusion over whose shirt Amrabat was accusing Geiger of pursuing. The original quote to NOS is not definitive, and FIFA's statement referenced Portugal's captain -- Ronaldo -- following initial reports of the interview in Netherlands, where Amrabat was born and raised. But Dutch reports on Thursday say the original interviewer has since clarified that Amrabat was saying he was told Geiger had asked for Pepe's shirt.

Another Morocco player, midfielder Karim El Ahmadi, criticised Geiger's performance after the game, saying Ronaldo's fourth-minute goal should not have been awarded because a foul was committed.

Geiger was the subject of further controversy on Thursday as he worked as the VAR for the game between Denmark and Australia, and suggested the match official look at a penalty decision that allowed the Socceroos to score and secure a 1-1 draw.

Together with the accusations, Amrabat's concussion meant he was the subject of two different critical FIFA statements in one day. Regarding his quick return after a head injury, FIFA said it would "address this matter with the Moroccan [federation] and, speaking in general terms, FIFA will monitor closely this matter throughout the competition."

Geiger, 43, is a longtime Major League Soccer referee who worked three games at the 2014 World Cup, at which he became the first American to officiate a game in the tournament's knockout rounds when he oversaw the round-of-16 match between France and Nigeria.

He was criticised after that game by then-Nigeria manager Stephen Keshi for a foul by France's Blaise Matuidi that forced Nigeria's Ogenyi Onazi to leave the match.

Geiger also refereed the 2015 Gold Cup semifinal between Mexico and Panama and later admitted to making errors during the match that impacted the outcome, with Mexico winning 2-1 in extra time en route to winning the tournament.