Kunowski was on the run from Poland at the time of the murder
A convicted killer dubbed "the Beast" who raped and murdered a 12-year-old girl has died in prison.
Police say Andrzej Kunowski died of heart failure on Wednesday at Frankland prison, Durham, where he was serving a life sentence.
He was jailed at the Old Bailey in 2004 for killing Katerina Koneva at her home in Hammersmith, west London, in 1997.
Police say he has also been linked to numerous investigations, including the disappearances of two young women.
He had previously served 10 years in jail in his native Poland where he became known as "the Beast" for 27 serious sex attacks on girls and women from the age of 17.
Police in West London say he is a suspect in the disappearances of 19-year-old student Elizabeth Chau in 1999 and Lola Shenkoya, a 27-year-old who vanished on her way home from work in 2000.
Detectives say they particularly want to speak to anyone who may have shared a cell with Kunowski during his time in prison.
Kunowski's trial was told he was on the run for raping a 10-year-old girl in Poland at the time of the murder.
Following his conviction in March 2004, Det Ch Insp David Little said: "He is probably the most dangerous sex offender I have ever come across and certainly the most prolific."
Katerina was strangled at her home on 22 May 1997 after she returned from school. Her father, Trajce Konev, came face to face with an intruder when he returned home and chased him into the street.
Kunowski was charged with murdering the girl when his DNA, which was taken after he was arrested for raping a student, matched a hair found on Katerina's cardigan.