Members of Ethiopia's security service have come under the spotlight over their involvement in a grenade attack at a rally attended by the prime minister.

Reuters reports that Ethiopia's attorney general Berhanu Tsegaye on Monday accused members of the National Intelligence and Security Service (NISS) of involvement in the blast that killed two people in June.

The attack happened shortly after reformist prime minister Abiy Ahmed left the stage.

Under other investigations, Berhanu added, arrest warrants have been issued for 36 security agents accused of rights abuses and corruption, and for more than 30 officials from a military-run firm, where he said inquiries had uncovered mismanagement.

“For six years, Metals and Engineering Corporation (METEC) made international procurement totaling $2 billion without any bidding processes,” Berhanu is reported saying, without naming the international firms involved.

The attorney general said the investigation involved METEC's procurement procedures and its contract for the Grand Renaissance Dam, the centerpiece of Ethiopia's bid to become Africa's biggest power exporter.