The chief adviser to the President has been killed and the Finance Minister injured in a plane crash near the eastern town of Bukavu.
The accident, the latest in a country with one of the world's worst air safety records, comes as Joseph Kabila braces for negotiations to form a new coalition government after his disputed victory in a chaotic election in November.
Augustin Katumba Mwanke, 48, was regarded as "the power behind the throne" in the Democratic Republic of Congo, according to a leaked 2009 US diplomatic cable published by WikiLeaks.
Four others died in the crash on Sunday – both American pilots and two people who were hit by the wreckage – said the Deputy Prime Minister, Adolphe Lumanu.
Mr Lumanu said Finance Minister Matata Ponyo Mapon, roving ambassador Antoine Ghonda and South Kivu governor Marcellin Chisambo Rohuya were also hurt when the privately owned Gulfstream jet crashed, although their injuries did not appear to be life threatening.