Berhanu Tsegaye, the attorney general of Ethiopia, announced the arrest of dozens of security forces and officials in a crackdown on corruption and human rights violations with the political establishment on Monday.
The attorney general laid out three sets of charges relating to human rights abuses, a grenade attack at a political rally, and corruption inside a military-run company. In total, 63 people were arrested.
Reports of arrests emerged in local media from Friday, but the full scope of the attorney general's investigation was not revealed until Monday.
Mr Berhanu said that a five-month-long investigation into the procurement process for the military-run conglomerate Metals and Engineering Corporation, Metec, has revealed vast corruption leading to the arrest of 27 people.
The attorney general said the company issued $2 billion worth of projects improperly.
"For six years Metec made international procurements totalling $2 billion without any bidding processes," Mr Berhanu told a news conference after announcing the arrest of several dozen security officials.
Some 36 of the country's intelligence service officers have also been arrested on charges of human rights violations, including murder, rape and castration, the Addis Standard reported.
Mr Berhanu's investigators found seven dungeons in Addis Adaba used for torture, the newspaper said.
He also said officials from the National Intelligence Security Service instructed an ethnic-Oromo group to conduct a grenade attack on the country's Prime Minister in June, killing two.
Earlier, the country's attorney general filed terrorism charges against five suspects from the Oromo Liberation Front for their involvement in the grenade attack.
The country's attorney general said the investigation of Metec involved a $4.8 billion contract for the Grand Ethiopian Renaissance Dam (Gerd), a huge infrastructure project, set to be the largest in Africa and triple the country's energy output.
In August, the government of Abiy Ahmed, Ethiopia's reformist prime minister, cancelled a contract with Metec to install the turbines of the dam, citing complaints of delays.
Metec is seen by some in the country as an arm of political influence of the small Tigrayan elite, who make up 6 per cent of the population. Mr Abiy is the first prime minister to come from the Oromo community, which makes up a third of the population.
Ethiopia is in the midst of a dramatic set of reforms, including normalising relations with former foe Eritrea, promoting the role of women and encouraging investment in the region.