Five people living in the UK are being investigated by Scotland Yarddetectives after a referral from Rwanda over allegations relating to the genocide 25 years ago.
An estimated 800,000 Rwandans, mostly Tutsis but including some moderate Hutus, died in 100 days of slaughter and ethnic cleansing between April 7 and July 1994.
The war crimes unit, part of the counter-terrorism command, received a referral from Rwandan authorities in January last year, a spokeswoman for London's Metropolitan Police confirmed.
It related to five individuals in the UK and allegations of genocide offences in Rwanda dating from around 1994, she said.
"Relevant documentation to this was assessed by the war crimes unit and officers were also deployed to Rwanda as part of our initial work to scope the allegations," the spokeswoman added. "As a result, we have subsequently commenced an investigation which will initially involve a review of all the documentation transferred from Rwanda.
"Given the complexities involved, this is expected to be a protracted and lengthy process. Inquiries continue."
The suspects are Celestin Mutabaruka, 63, from Kent; Vincent Brown, also known as Vincent Bajinya, 59, from Islington, north London; Celestin Ugirashebuja, 66, from Essex; Charles Munyaneza, 61, from Bedford; and Emmanuel Nteziryayo, from Manchester, the Daily Mirror reported.
All five deny the allegations against them and involvement in the genocide.
In July 2017 five men with the same names, all of Hutu ethnicity, had an extradition bid to have them returned to Rwanda blocked by the UK High Court.
At the time judges agreed there was a real risk they would be denied a fair trial if they were returned.
2019, The Independent