Spanish prosecutors opened a probe on Monday into racist chants hurled at Real Madrid's star forward Vinicius Junior during a match as the football federation president admitted the country had a "problem" with racism.

The 22-year-old Brazilian international forward was targeted by a home supporter during a 1-0 defeat at Valencia on Sunday and was later sent off.

The prosecutor's office in Valencia is investigating the incident as a possible "hate crime", a judicial source told AFP news agency.

The move comes after Real Madrid said it had filed a complaint with the office "in order for the facts to be investigated and for those responsible to be held accountable."

The club said the chants, in its view, "constitute a hate crime".

Top figures from the world of football and beyond rallied around the player, who has frequently been singled out for racial abuse in La Liga.

The head of Spain's football federation, Luis Rubiales, said the country had a "problem" with racism.

"As long as there is just one fan, a single undesirable, or group of undesirables who hurl insults over someone's sexual orientation, or skin colour, we have a serious problem," he added.

Vinicius stood in front of fans behind the goal and pointed to the apparent culprit and play was delayed for several minutes in the second half.

Referee Ricardo de Burgos Bengoetxea spoke to stadium officials, who made an announcement calling for racist insults to stop before play resumed 10 minutes later.

The referee wrote in his post-match report that a fan shouted "monkey, monkey" at the player.

Vinicius was sent off in added time at the end of the game for hitting Valencia player Hugo Duro during a brawl.

He issued a statement afterwards saying that La Liga "belongs to racists" and several Brazilian players past and present offered their support.

Brazilian President Luiz Inacio Lula da Silva condemned the abuse, telling a news conference at the close of the G7 summit in Hiroshima: "He was attacked. He was called a 'monkey'."

Spain's Labour Minister Yolanda Diaz, a deputy prime minister, also weighted in, saying "racist chants in football stadiums do not represent our country".

"We will continue to work to end racism," she tweeted. (AFP)