Fayulu made the remarks during a press conference in Brussels, Belgium, where he argued that the Banyamulenge are not Congolese.
He said ethnic groups in the Democratic Republic of Congo (DRC) have their own languages, but claimed that the Banyamulenge do not because they speak Kinyarwanda, which he used to argue that they originate from Rwanda.
'Which Congolese person does not have a language? Raise your hands. Is Kinyamulenge a language spoken in Congo? They speak Kinyarwanda,' Fayulu said.
He went on to question whether the Banyamulenge are among the ethnic groups that make up the DRC.
'Are the Banyamulenge Congolese? Look at the ethnic groups in Congo. There is no such ethnic group,' he said.
Amb. Nduhungirehe condemned Fayulu's remarks, drawing a comparison with rhetoric used by a section of Rwanda's political class in the years leading up to the 1994 Genocide against the Tutsi.
'Ethnic hatred, historical distortions and cynical remarks have reached a worrying level within the Congolese political class, including part of the opposition,' Amb. Nduhungirehe said.
'This strangely reminds me of a section of Rwanda's political class between 1990 and 1994 which, as part of a genocidal process of delegitimisation, claimed that Rwandan Tutsi were not true indigenous people,' he added.
In the years preceding the Genocide against the Tutsi, extremist propaganda sought to portray Tutsis as foreigners who had taken control of Rwanda.
In November 1992, Léon Mugesera, a prominent figure in the then-ruling MRND party, delivered an inflammatory speech in Kabaya, in the former Gisenyi Prefecture, in which he called for Tutsis to be sent back to 'Abyssinia' through River Nyabarongo.
Questions surrounding the citizenship and identity of the Banyamulenge have remained a longstanding source of political controversy in the DRC.
Human Rights Watch has documented how, particularly during the 1980s and 1990s, some politicians in then-Zaire sought to strip Banyamulenge of citizenship by portraying them as immigrants from Rwanda.
Amb. Nduhungirehe also criticised those who give platforms to politicians making such statements, warning that they could eventually be held responsible for doing so.
'At some point, those who roll out the red carpet for these unscrupulous politicians, instead of taking action against them, will also have to answer for it,' he said.
