Detectives are investigating three alleged murders as part of an inquiry into historical child abuse, the Met Police has said.
Police say no confirmed identities or bodies of victims had been found.
Officers made a public appeal for information relating to Dolphin Square estate in Pimlico, south-west London, amid claims boys were abused there.
Allegations of a paedophile ring involving prominent figures in the 1970s and 1980s are being investigated.
The appeal was made as part of Operation Midland, which is under the umbrella of Operation Fairbank, and is one of a number of ongoing inquiries into historical abuse.
The paedophile ring is alleged to have included senior military, law enforcement and political figures.
Deputy Assistant Commissioner Steve Rodhouse said police were examining whether children were abused at locations across London, in the Home Counties and at “military establishments”.
BBC home affairs correspondent Tom Symonds said it was the first time Operation Midland had confirmed the number of possible murders officers were investigating.
He said the allegations were that the murders involved three children. The claims also included allegations a child had been run over.
Police said the inquiry was working through historical missing persons reports and unsolved child murders to look for possible links to the case.
However, officers said the search was being hampered by out-of-date records from the past.
The operation stems from allegations made by a man known as “Nick”, who says he was abused by a paedophile ring including high-profile people from the age of seven to 16.
He has told police he was taken by car to “parties” where he was abused by a man on his own, as well as a group of men, at a flat in the Dolphin Square estate.
Asked about the claims, Det Supt Kenny McDonald – who is overseeing Operation Midland – said officers who had spoken to him thought his account was “credible and true”.
“Nick has described how a car would be sent to collect him, and he would be driven to Dolphin Square,” he said.
He told the BBC the alleged abuse Nick had described was “horrendous and horrific”.
Det Supt McDonald also appealed for other boys who might have been abused to come forward.
“I believe that there were other boys who were abused, or who were present while the abuse took place,” he said.
“I would ask you to trust me. I will support you, and do everything in my power to find those responsible and bring them to justice. I need your accounts to help me do that.”
It comes after Nick gave his first broadcast interview last month, telling the BBC his abusers had no hesitation in doing what they wanted.
“Some of them were quite open about who they were. They had no fear at all of being caught, it didn’t cross their mind,” he said.
The abusers “created fear that penetrated every part of me, day in day out”, he added.
“You didn’t question what they wanted, you did as they asked without question and the punishments were very severe.
“They were very powerful people and they controlled my life for the next nine years,” he told the BBC.
Scotland Yard detectives have spoken to the family of Martin Allen, who disappeared in 1979 at the age of 15, police confirmed.
Police were also in close contact with Sussex Police, where officers are carrying out a further review into the disappearance and murder of eight-year-old Vishal Mehrotra in 1981.
Officers said it was not possible to say whether either disappearance was linked to Operation Midland, which was launched by the Met’s homicide and major crime team last month.
It is part of the wider Operation Fairbank, which is investigating allegations of abuse involving senior politicians and high-profile figures.
The inquiry was set up in response to allegations made by Labour MP Tom Watson in the House of Commons and has received more than 600 emails and pieces of information about alleged abuse.
It comes after the government launched two inquiries into historical child sex abuse allegations.
David Gibbs, Chartered Legal Executive at specialist child abuse solicitors Jordans said “Tragically, the news that homicide detectives are involved in a case of historic child abuse is not unsurprising. We have dealt with many cases where there have been allegations of child murders and cover-ups by those involved in the mass abuse of children.
“We would urge anybody with information relating to this current operation to contact the Metropolitan Police to assist with their investigation and bring those responsible to justice.”