A doctor is accused of being a party to six genocide murders, including the stoning to death of a taxi driver and the killing of a woman and her child.
Dr Vincent Brown, formerly Dr Vincent Bajinya, 65, was allegedly a "supervisor" of violence carried out by others in Rwanda in 1994.
The claims were heard at Westminster Magistrates' Court on Tuesday.
Dr Brown lived in the capital Kigali during the notorious genocide of the minority Tutsi population, in which an estimated one million people died.
The court heard the then 33-year-old was head of the family health department in the city.
Prosecutor Jane Stansfield alleged he was a "leader or supervisor" of physical acts of violence which were carried out by others.
She told the court he led a group to a house on 8 April 1994 and ordered the shooting of three people: Dominique Mukurarinda, Immaculee Mukankusi and Gerase Rurangirwa.
In the days after, he allegedly directed a group to kill Leandre Mbogoye, who was stoned to death; and on 10 April ordered the murders of Charlotte Kamaguja and her infant son Olivier Tuyishime.
The defendant has been charged with conduct ancillary to genocide and six counts of conduct ancillary to murder as a crime against humanity.
Dr Brown - who lives in Islington, north London - spoke only to confirm his name, date of birth and address.
His lawyer said he denied the charges and wanted to prove his innocence.
He was granted conditional bail - which included a £25,000 bond and surrendering his passport - and will appear next at the Old Bailey on 9 October.
It's the first prosecution of its kind in the UK and charges were brought after a seven-year investigation by the Met Police's war crimes team at the request of the Rwandan government.
The allegations relate to a genocide in the Rugenge district of Kigali.
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In a statement, Frank Ferguson, head of the CPS special crime division, said Dr Brown had allegedly "directed and incited acts of murder and genocide carried out by others".
Commander Helen Flanagan, head of counter terror policing in London, said the case showed "the UK is not a safe haven for individuals suspected of committing international crimes" and people accused of atrocities would be held accountable.
She said a number of other Rwanda genocide investigations were ongoing.
(c) Sky News 2026: Doctor was 'supervisor' of killings during Rwanda genocide, court hears
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