The attack in the capital on June 22 injured more than 150 and raised fears that a group or individual may want to use violence against Abiy, who has presided over a series of reforms and a rapprochement with Eritrea since taking power in April.

Federal prosecutors gave details of those to be charged but did not elaborate on a possible political motive for the attack.

They said a suspect named Getu Girma is accused of orchestrating the attack. He is previously unknown to the public, but they said he had spent two years in jail before an amnesty secured his release, according to the state-run Ethiopian Broadcasting Corporation.

A second suspect is accused of attempting to help the attackers escape police custody while they were being treated for blast wounds.

A third, who is female, has claimed insanity and is undergoing psychiatric evaluation, the broadcaster said, adding that a court granted prosecutors 15 days to lodge charges following the end of the police investigation.

Nine others, including the deputy head of Addis Ababa’s police commission, are being held for security lapses.

Abiy had just finished a speech to tens of thousands of supporters in Meskel Square when the grenade exploded, prompting his security officers to whisk him away.

Since taking office, Abiy has loosened the state’s grip on some economic sectors, extended an olive branch to dissidents overseas, acknowledged abuses by security services and ended a military stalemate with Eritrea. He has also replaced several heads of the security services.