In a document dated May 28 seen by AFP, Judge Carmel Agius of the Mechanism for International Criminal Tribunals (MICT) said he had instructed the court registrar "to transfer Ngirabatware to Senegal for the enforcement of his sentence as expeditiously as possible" after the conclusion of a separate case.
Ngirabatware was the Minister of Finance and Economic Planning between 1990 and 1994.
He was convicted in December 2012 for inciting, aiding and encouraging Interahamwe militiamen in his home district of Nyamyumba in northwestern Rwanda to kill and rape their Tutsi neighbours.
An initial sentence of 35 years was reduced to 30 years in 2014 after the rape conviction was set aside. The sentence was otherwise confirmed in a review in 2019.
In the separate case, Ngirabatware and three others were found guilty on July 25 of having tried to bribe or intimidate witnesses to have his conviction overturned.
Ngirabatware, a Swiss-educated economist born in 1957, is the son-in-law of Felicien Kabuga, a major figure who is accused of having bankrolled the 1994 Genocide against Tutsi. He was arrested in a suburb of Paris in May 2020.
The sentence against Ngirabatware was handed down by the International Criminal Tribunal for Rwanda (ICTR), which closed down in 2015, handed over its work to the UN-backed MICT.
Ngirabatware fled Rwanda in July 1994, finding work in research institutes in Gabon and France before being arrested in Germany in 2007 and transferred to the ICTR the following year.