Rwanda has expelled the German ambassador from its capital city of Kigali in retaliation for the arrest of a senior Rwandan official in Frankfurt on Sunday.
The official, Rose Kabuye, was detained on a French warrant, accused of involvement in the shooting down of an airliner in Rwanda in 1994.
The plane was carrying Rwanda's Hutu president at the time, Juvenal Habyarimana, and his death is regarded as the main trigger of the subsequent genocide.
A spokesperson with the Prosecuting Office in the German state of Hesse, Hildegard Becker-Toussaint, says the charges against Ms Kubuye are being taken very seriously.
The Rwandan government says it has also recalled its ambassador from Germany.