A convicted killer dubbed "the Beast" who raped and murdered a 12-year-old girl in Hammersmith has died in prison.

Police say Andrzej Kunowski (pictured) from Twyford Avenue in Acton 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.

Kunowski followed Katerina from school and entered the family home in Iffley Road, Hammersmith on Thursday 22 May 1997. He barricaded the living room door and strangled Katerina with a ligature, which he had formed into a garrotte.

He jumped from the first floor and fled the scene after being disturbed by Katerina's father, Trajce Konev. He ran off but was chased by Mr Konev - who thought he was a burglar.

Kunowski hijacked a black Fiat Uno, threatening the woman driver with a knife. He abandoned the car and got on a bus which took him to Hammersmith Broadway, where he was last seen.

Police issued numerous appeals to the media and via Crimewatch. Eventually in May 2003, Kunowski was convicted of a rape committed in Acton in September 2002. He received nine years imprisonment at HMP Belmarsh and his DNA submitted to the national database. It was found to match that found on Katerina's clothing.

Kunowski was sentenced to a whole life order term imprisonment.

Kunowski 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 and has been linked to numerous other enquiries.

Police are now investigating possible links between Kunowski and the disappearance of two women from the Ealing area.

Police questioned Kunowski about Thames Valley University student Elizabeth Chau,19, who vanished near her home in Ealing five years ago and Lola Shenkoya,27, who went missing in the area January 2000.

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."

Despite his death police are still keen to speak to anyone who knew Kunowski or has information about crimes he may have committed.

DI Andy Manning, Homicide and Serious Crime Command said:

""Now that Kunowski is dead I am hoping that anyone who was too scared to come forward previously will come forward and speak to us with any information about him which could help us piece together evidence with regard to other crimes he may have committed.''

Anyone with any information should contact the MPS Homicide & Serious Crime Command on 0208 358 0300 or call Crimestoppers on 0800 555 111.