ADDIS ABABA (Reuters) - Ethiopian prosecutors on Wednesday charged the former president of the Somali Region and 46 others with instigating ethnic violence there last year, as the new prime minister cracks down on the security services and senior members of past administrations.

The arrest last August of Abdi Mohammed Omer, who spent more than a decade in charge of the vast gas-rich region that shares a border with Somalia, came amid sweeping reforms since the appointment in April of Abiy Ahmed as prime minister.

The 42-year old Ahmed has promised to rein in the powerful security services and made peace with separatist groups including ONLF rebels whom Abdi had spent years trying to crush.

Rights groups regularly accused Abdi’s administration of abuses including torture during and after the fight with the insurgents.

Last year, 58 people died and more than 250 were injured when violence broke out in Jijiga, capital of Somali Region.

According to the five-month federal investigation that resulted in Abdi and 46 other officials being charged, organized mobs were ordered to “kill, loot and destroy” non-ethnic Somali residents and their properties.

Abdi and the other officials were charged with “direct or indirect involvement” in instigating ethnic Somalis to take up arms against non-Somalis.

The defendants “organized a youth group and disseminated messages to kill all other non-Somalis, as well as to seize and destroy their properties, loot banks and insurance firms, and burn down churches and petrol stations”, according to the charge sheet seen by Reuters.

Abdi, who appeared in court alongside five other political and security officials from his administration, was separately charged with attempting to “overthrow the constitutional order”.

All of those charged are due to appear in court on Feb. 6 to enter pleas. Most of the officials were heads of departments in the regional government or in other senior political and security roles.

Details of the investigation disclosed last week by the Federal Attorney General’s office described how the regional government presided over a litany of horrific crimes, including beheadings, torture of opponents, and mass rape.

It said police had uncovered a grave containing at least 200 bodies along the border with Oromiya Region, as well as another one with more than 50 corpses.