Arthur
Arthur has a €50m release clause in his contract. Getty

Barcelona have issued an apology to Gremio after a photograph of Arthur Melo wearing the Catalan shirt alongside club technical secretary Robert Fernandez caused a big controversy over the weekend.

The 21-year-old midfielder has been heavily linked with a January move to the Nou Camp in recent days after it emerged that Fernandez had travelled to South America to watch him in action during the Copa Libertadores final between Gremio and Lanus.

The Brazilian starlet especially impressed the Barcelona chief during the second leg, producing a Man of the Match performance to help Gremio secure a 2-1 win and claim the title with a 3-1 victory on aggregate.

Last week, Sport claimed that Manchester United and other European clubs were also monitoring the situation but Barcelona had taken the lead in the race after Fernandez met with Arthur's agent to discuss his move to the Nou Camp.

The saga took a major twist over the weekend after a picture of Arthur wearing the Barcelona shirt alongside Fernandez was leaked.

Gremio president Romildo Bolzan expressed his disappointment with the La Liga giants hours later, saying that they will need to pay Arthur's full €50m (£44.1m, $59.2m) release clause if they are to sign him.

"Arthur is under contract with Gremio and his release clause is €50m," Gremio president Romildo Bolzan told RAC1.

"If a club pays that then we are unable to stop him going but as things stand there are no talks about that and there are no ongoing negotiations. We were told that Arthur was going to eat with some Barcelona representatives and we gave this the green light as we believed it was just to meet family and nothing more. We are not comfortable at all with this situation."

Gremio chief Andre Zanotta has revealed that on Saturday Fernandez himself called him to apologise with hopes to make amends with the Brazilian outfit.

"Yesterday (on Saturday 3 December), Robert Fernandez called me. He apologised. Robert was in Porto Alegre. I relayed the apology to president Romildo. We think there is no reason to put a shirt on someone who has a contract until 2021, "Zanotta said to Globo Esporte.

"They admitted the interest [in Arthur], of course, but they said they would talk to Gremio [if they want to sign him]. He has release clause. Whoever wants to talk will listen. There is no a concrete proposal from Barcelona or any other team."

Barcelona will be hoping Gremio agree to negotiate the transfer below his release clause but Globo Esporte points out that Brazilian outfit have already rejected an offer worth €35m to part ways with his services.

The Brazilian publication doesn't reveal which club was behind that offer but earlier this month, the Daily Mail reported that, alongside United, Chelsea and Atletico Madrid were also monitoring the situation.