Five people were Friday charged with terrorism for the Addis Ababa rally bombing attended by Prime Minister Abiy Ahmed in June.
The Attorney General said the grenade attack was planned by members of the Oromo Liberation Front (OLF) with the intent to assassinate the Ethiopian leader because they believed he was not popular among the Oromos, the largest ethnic group, and would not act in their interests.
The prosecutor said that an Ethiopian woman named Genet Tamiru, also known as Toleshi Tamiru, was the mastermind of the attack and that she is based in Nairobi, Kenya.
The five suspects, who have been in custody, arraigned on Friday are Getu Girma, Birhanu Jafar, Tilahun Getachew, Bahiru Tolosa and Dessalegn Tesfaye.
Two people were killed and more than 150 others wounded in the explosion in Meskel Square on June 23 that occured near the stage soon after Dr Abiy delivered a speech to tens of thousands of supporters.
The Prime Minister, an ethnic Oromo, has pursued reforms and reconciliation with various opposition and outlawed groups since coming into power in April this year.
OLF, which had been ban for insurgency, was recently removed from the country's terrorist list and its exiled leaders pardoned and welcomed back to Addis Ababa.
OLF has not made any comment regarding those charged in court.