Croatia goalkeeper Danijel Subasic was issued a warning by FIFA after his team's World Cup victory over Denmark for revealing a T-shirt with a message honouring a former teammate who died a decade ago from injuries suffered during a match.

Subasic, 33, saved three penalties in Sunday's round-of-16 shootout win in Nizhny Novgorod, and afterward showed the tribute to close friend Hrvoje Custic, who died in 2008 after being injured during a game falling into a concrete wall near the sideline of a field.

"A warning has been issued for such violation as well as for the infringement of the FIFA Equipment Regulations due to the display of a personal message by the player Danijel Subasic after the end of the said match," FIFA said in a statement released on Thursday.

Subasic's tribute to Custic, his former teammate at hometown club Zadar, came after a win that booked Croatia a quarterfinal place against hosts Russia in Sochi on Saturday.

Croatia goalkeeper Danijel Subasic revealed a tribute to former teammate Hrvoje Custic after the win over Denmark. Getty

At a news conference at Croatia's team base in Sochi on Tuesday, Monaco goalkeeper Subasic broke down in tears when asked about his friend.

"That's what happens," Subasic said through tears. "What happened to him, you know the story. I don't think from my side there is need for extra explanation on that question."

Emotions are still raw for #CRO goalkeeper Danijel Subasic about the death of a teammate from an on-field injury a decade ago #WorldCup @ByTimBooth https://t.co/m9cGqbQThV pic.twitter.com/CrXeiiYIIo — AP Sports (@AP_Sports) July 3, 2018

Croatia defender Domagoj Vida, also attending the news conference, comforted his teammate and added: "He has a great positive energy about him, and he's always showing his emotion, including today."

FIFA said in the same statement on Thursday that it had fined Croatia's football federation 70,000 Swiss francs ($70,500) for an ambush marketing incident by players during the game -- a seven-fold increase on the fine FIFA imposed on Russian football's governing body for a fan's neo-Nazi banner at a match.

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FIFA said its disciplinary panel fined Croatia for "the display of non-authorized beverage products" by players during their round-of-16 win against Denmark on Sunday.

Longtime FIFA partner Coca-Cola has exclusive rights to supply its brands at World Cup stadiums and sites.

Information from the Associated Press was used in this report