Prime Minister Abiy Ahmed's office named Amhara security chief Asaminew Tsige as the chief suspect in an "attempted coup" in the region that left its president, top adviser and attorney general dead on Saturday.
A few hours later in what the government said appeared to be a "co-ordinated attack", the army chief Seare Mekonnen was killed by his bodyguard at his home in Addis Ababa.
However details of links between the two attacks and their ultimate motive have not been made clear.
"Asaminew Tsige, who has been in hiding since the failed coup attempt over the weekend has been shot dead”, state broadcaster EBC reported, saying it had happened in the regional capital Bahir Dar.
While observers say there were no clues indicating a concerted national coup, the unrest is a major blow for Abiy, who has embarked on a series of reforms which have unleashed ethnic tensions and bitter political rivalries.
Released from prison last year
Asaminew was released last year after almost ten years in prison over a 2009 coup plot, under a mass prisoner amnesty that began under former Prime Minister Hailemariam Desalegn and continued under his reformist successor Abiy.
Analysts describe him as a hardline Amhara nationalist who was facing possible removal from his job over efforts to form a militia as well as rhetoric pushing for territory in neighbouring Tigray to be reclaimed.
He recently appeared in a Facebook video calling for civilians to arm themselves in preparation for attack.
Amhara is one of Ethiopia's nine autonomous states and its people are the second-largest ethnic grouping after the Oromo.
Both communities spearheaded two years of anti-government protests which led to the resignation of Hailemariam.
The European Union in a statement has urged "restraint from all sides of the Ethiopian political spectrum, both at national and regional levels."
Observers have said that the killings underscore the tensions across Ethiopia sparked by Abiy's efforts since he came to power in April 2018 to loosen the iron grip of a state long run by strongmen.
His efforts to transition from one-party state to democracy have seen him embarking on economic reforms. He has allowed dissident groups back into the country, sought to crack down on rights abuses and arrested dozens of top military and intelligence officials.
These moves have been lauded abroad, but have earned Abiy enemies at home. Exactly a year ago he survived a grenade attack at a rally which left two dead.