A farmer converted into a businessman, Munyakazi, 74, is the oldest of the people currently held in special detention facility by the ICTR, mandated by the UN Security Council to try key suspects of worst modern century tragedy.
Prosecuted for genocide, or, alternatively complicity to genocide, and extermination, the accused has pleaded not guilty.
In his opening statement, Richard Karegyesa, from the office of the prosecutor, underlined the active participation of the old man in the massacres of Tutsis in the prefectures of Cyangugu and Kibuye, western Rwanda.
Between 13 and 30 April 1994, the Ugandan lawyer alleges, the defendant directed four attacks against Tutsis who had sought refuge in the cathedral of Cyangugu and in other Catholic churches.
All these attacks, he added, Munyakazi and his Interahamwe militiamen, whom he had recruited, trained and armed, killed Tutsis using firearms, grenades or machetes.
In the opinion of the prosecution, this follower of Islam was so dedicated to the massacres that he left in reinforcement on 30 May 1994 to the Bisesero heights, in the prefecture of Kibuye, where Tutsis held a resistance to the attackers.
As the attorney was charging him, Munyakazi, noticeable by his long white beard and his Muslim red-and-white head-scarf, followed carefully the allegations, without blinking.
These charges were translated for him into Kinyarwanda, because he does not understand French or English, the two official languages of the Tribunal.
After his opening statement, Karegyesa called his first witness, a man who began his testimony in closed session.
Munyakazi was arrested in May 2004 in eastern Democratic Republic of Congo (DRC), where he pretended to be an Imam under the name of Mzee Mandevu (literally, the bearded old man in Kiswahili).
Munyakazi is defended by Professor Jwani Mwaikusa from Tanzania who last year successfully challenged the accused's transfer to Rwanda for a trial.
Munyakazi's trial is the second to start this year, after that of Lieutenant Ildephonse Hategekimana.
Hategekimana was also among five targeted by a transfer request to Rwanda, which was rejected by the ICTR judges.
Seven other prisoners, including two former ministers, are still waiting to appear, whereas the Security Council has insisted that the ICTR must finish all first instance trials by end of this year.
© Hirondelle News Agency