With the World Cup barely a month away, Brazilian superstar Neymar went on trial in Spain on Monday over alleged irregularities in his transfer to Barcelona nearly a decade ago.

Wearing sunglasses and a dark suit, the 30-year-old waved to the press as he arrived at the Provincial Court of Barcelona with his parents, who are also in the dock.

He will likely take the stand on Tuesday. The player had been set to testify on either October 21 or 28 but the judge agreed to bring forward his hearing to avoid a clash with his football commitments.

Spanish prosecutors are seeking a two-year prison term for Neymar and the payment of a fine of 10 million euros.

The high-profile trial is the culmination of a years-long legal saga over his 2013 transfer from the Brazilian club Santos to Barcelona.

He later joined Qatar-owned Paris Saint-Germain in a world record 222 million euro transfer in 2017.

Neymar, who arrived in Barcelona early on Monday, spent two hours at the court before he was excused by the judge for the rest of the day's hearing after his lawyers argued he needed to rest.

The player scored the winning goal against Marseille in a Ligue 1 match on Sunday night.

He is one of nine defendants on trial on corruption-related charges, among them his parents and their N&N company, which manages his affairs.

Investigators began probing the transfer after a 2015 complaint filed by DIS, a Brazilian company that owned 40 percent of the player's sporting rights when he was at Santos.

Barcelona said the transfer cost 57.1 million euros, but prosecutors believe it was at least 83 million euros.

The club said it paid 40 million euros to N&N and 17.1 million to Santos, of which 6.8 million was given to DIS.

But DIS alleges that Neymar, Barcelona and the Brazilian club colluded to mask the true cost of the deal. It is seeking to recover 35 million euros.

Neymar's lawyers insist their client is innocent, saying the 40 million euros was a "legal signing bonus which is normal in the football transfer market".

They have said Spanish authorities lack jurisdiction to hear the case since the transfer involved Brazilian nationals in Brazil.

The trial is due to end on October 31. (AFP)