Rwanda's intelligence chief will appear in court today in connection with alleged war crimes.
Karenzi Karake was detained by the Metropolitan Police's extradition unit on behalf of authorities in Spain, where he is wanted over alleged crimes against civilians.
The 54-year-old director-general of Rwanda's national intelligence and security services is due to appear in custody at Westminster Magistrates' Court.
He is accused of ordering massacres while head of military intelligence in the wake of the 1994 Rwanda genocide, and of ordering the killing of three Spanish nationals working for aid charity Medicos del Mundo.
But his arrest on Saturday was condemned by Rwanda's high commissioner in London.
Williams Nkurunziza, Rwanda's High Commissioner to the UK, called the arrest "an insult" and former international development secretary Andrew Mitchell claimed it was "politically motivated".
Mr Mitchell, who worked closely with the Rwandan government while a Cabinet minister, said the European arrest warrant system was being "abused", with the allegations pursued by supporters of the old regime in Rwanda.