Sadistic gangsters tortured and killed a treacherous gang member then turned him into a stew, police believe.
They are thought to have beaten Milan Jurisic, 37, to death with a hammer, skinned and boned him with a sharp knife then put him through a meat grinder.
Their hitman, Sretko Kalinic, nicknamed The Butcher, confessed to the crime after being arrested in the Croatian capital Zagreb last year.
He said he ‘literally dismembered him’ in order to turn the body into mincemeat and throw any remains into the river in Madrid.
Spanish officers this week found 50 bones in the Manzanares river and located the house of horrors where the bloodbath took place.
They are awaiting forensic confirmation that the bones are those of Jurisic.
The cannibal gang is also said to have made a sinister face mask from the victim’s skin before eating him for lunch.
The killers are believed to have spent the next five days cleaning the premises where the murder took place.
Jurisic was on the run after being convicted in his absence to 30 years in prison over the assassination of Serbian prime minister Zoran Djindjic in 2003.
Police believe the gang which killed him was led by Luka Bojovic, who was arrested last month and also accused of assassinating Mr Djindjic.
Inside Bojovic’s apartment in Valencia they found documents backing up Kalinic’s account of the killing. Officers also found a letter suggesting Jurisic and Bojovic fell out over a woman.
Previously, it was thought their argument was over money.
All of those involved in the Madrid murder are said to be members of the Zemun Clan, a Serbian crime group from Belgrade.
The crime is being investigated at the National Court in Madrid.