Scotland Yard is investigating the alleged murder of three young boys linked to a Westminster paedophile ring active in the late 1970s and early 1980s.
Detectives have appealed for abuse victims and potential witnesses to come forward to assist them in their probe into the historic sex gang, codenamed Operation Midland.
Appealing for witnesses, the man leading the inquiry said people who lived in or visited Dolphin Square in Pimlico, central London, in the 1970s "will have seen or heard something that they only understand the significance of now".
The residential development near the UK parliament has long been popular with MPs.
Cyril Smith, the late Liberal MP, was among the senior politicians named in a 40-page dossier detailing alleged child abusers within the British establishment sent to then Home Secretary Leon Brittan in November 1983.
Police are also investigating allegations that abuse took place at other premises across London and the Home Counties, including some military bases.
Detective Superintendent Kenny McDonald, the lead officer for the operation, said: "I appeal to men who were subjected to abuse 30 years ago to come forward.
"We are also investigating the murder of three young boys - we are determined to find answers."
Deputy Assistant Commissioner Steve Rodhouse said an alleged victim, called Nick - not his real name - had claimed he was abused at a flat in Dolphin Square between 1975 and 1984.
Mr McDonald said: "Nick has been spoken to by experienced officers from the child abuse team and from the murder investigation team and they and I believe what Nick is saying is credible and true, hence why we are investigating the allegations that he has made."
"Nick" has alleged he was abused by single men, groups of men and at "parties", and that other young boys were present who were also abused, Mr McDonald added.
No further details of the alleged murders were given by detectives.
Mr Rodhouse said: "We are committed to fully investigating these cases and we will go where the evidence takes us and we will act without fear or favour."
Police have said they had not confirmed any identities of the murder victims and said no bodies had been found.
Detectives are now working through historical missing persons' reports and unsolved child murders to look for possible links to the case.
Last month, the father of an eight-year-old boy murdered 33 years ago claimed his son may have been killed by the paedophile ring.
(© Daily Telegraph, London)