Ethiopian state television announced Monday that Prime Minister Meles Zenawi died. He hadn't been seen in public for months.
A former rebel fighter, Meles took power in 1991 after toppling the dictatorship of Mengistu Haile Mariam.
The International Crisis Group, in a 16-page report, said Meles' ruling party made sweeping promises of social liberation and democracy but later relied on repression to quiet his opponents.
The government announced that Deputy Prime Minister Halemariam Desalegn would serve as interim head of state until 2015 elections. ICG states that the president's successor will face a wide range of struggles in the country, seen as a bulwark against regional al-Qaida affiliates.
The ICG reports that should conflict grow out of the power vacuum, it could spill across the Ethiopian borders.
"The regional implications will be enormous," the report stated. "Increasing internal instability could threaten the viability of Ethiopia's military interventions in Somalia and Sudan, exacerbate tensions with Eritrea, and, more broadly, put in question its role as the West's key regional counter-terrorism ally."