A 20-year old Spanish man who said a masked gang assaulted him with a knife in Madrid and carved a homophobic slur into his buttocks has since told police the injuries were consensual, the Interior Ministry said on Wednesday.

Protests had been called across Spain on Wednesday evening in response to the supposed attack, whose apparent brutality and proximity to the renowned gay-friendly neighbourhood of Chueca stunned Spanish society.

But the ministry, in a message sent to journalists, said the man retracted his initial claim that he was attacked in the central Madrid neighbourhood of Malasaña on Sunday and admitted the injuries he received were inflicted with his consent.

It would not comment on the man's motives nor reveal his identity. Reuters has not been unable to establish his identity either.

Protest organisers said Wednesday's rally would still take place.

Homophobic violence has been in the spotlight in Spain after the killing of nursing assistant Samuel Luiz, who was beaten to death in the northwestern region of Galicia in July allegedly because of his sexual orientation.

Interior Minister Fernando Grande-Marlaska warned earlier on Wednesday that hate crimes were on the rise and were becoming more violent.