Police detained seven men on Tuesday over separate alleged hate crime incidents against Real Madrid football player Vinicius Jr as Spain's main soccer league urged changes to Spanish law that would enable it to take steps to curb racism in stadiums.

Real Madrid manager Carlo Ancelotti expressed support for Vinicius Jr, whom he expected would remain at the club.

He lambasted Spain's "obsolete" protocols to deal with racism in the sport, and said he would consider taking his players off the pitch if they were to be abused again during a game.

Puma, sponsor of both Valencia and LaLiga, also offered its support to Vinicius Jr, as did Spanish bank Santander, whose title sponsorship with LaLiga ends after this season.

"At PUMA, we do not tolerate racism, we condemn discrimination in any form and stand in solidarity with Vinicius Junior," Puma said in a statement to Reuters.

A hate crime investigation was opened after an inflatable effigy dressed in the No. 20 jersey of winger Vinicius Jr was hung from a bridge in front of the club's training grounds. Alongside it was a 16m (17.5-yard) red and white banner - the colours of rival team Atletico Madrid - that read "Madrid hates Real".

Four men were arrested in Madrid, police said, three of whom were members of "a radical group of fans of a Madrid club", who were previously flagged during matches as "high risk" to help curb violence during games.

Three men were also arrested in Valencia for racist conduct aimed at Vinicius in a match between Valencia and Real Madrid, police said on Twitter.

After slurs were aimed at Vinicius Jr during a Spanish league match on Sunday, Vinicius Jr, in a social media post, called the racist abuse "inhuman" and asked sponsors and broadcasters to hold LaLiga accountable.

'IMPOTENT'

LaLiga said in a statement on Tuesday that it felt "impotent" to tackle the issue while Spanish legislation limited its actions to merely detecting and reporting racist incidents.

It urged that the law to be modified so that it could cancel matches and ban fans from stadiums if racist behaviour is detected.

"LaLiga is extremely frustrated by the lack of sanctions and convictions by sporting disciplinary bodies, public administrations and courts public administrations and the jurisdictional bodies to which complaints are made," it said in a statement.

Vinicius has expressed frustration that LaLiga has not exerted pressure on the Spanish football federation, which does have the power to apply stadium closures and bans, according to sources close to the player.

The federation can cancel a match if racist insults continue after a 10-minute period in which the game is paused and the crowd warned. To date, no match in Spain has enforced it.

The Brazilian player was particularly aggrieved by comments made by LaLiga President Javier Tebas on Sunday, in which he accused the player of failing to turn up to meetings so that LaLiga could explain what it has been doing to address racism, sources close to the player told Reuters.

Vinicius was initially receptive to a meeting if it was held behind closed doors, according to the sources, but turned it down believing the LaLiga administrator was seeking publicity by holding it at its Madrid offices.

LaLiga declined to comment on the proposed meeting with Vinicius while the football federation did not respond to a request for comment about its powers to cancel matches.

The federation and LaLiga said on Tuesday they were launching a campaign until the end of the season against racism.