Ethiopia's army chief of army was shot and killed by his own bodyguard during an attempted coup in a northern state on Saturday, Prime Minister Abiy Ahmed said on Sunday.
At least two leaders from one of the country's regional governments were killed in the coup bid and one other was wounded.
The prime minister's spokeswoman Billene Seyoum said a "hit squad" led by Amhara's security chief Asaminew Tsige burst into a meeting on Saturday afternoon and shot regional president Dr Ambachew Mekonnen and other top officials.
Then, later on Saturday, Gen Seare Mekonnen was killed by his bodyguard in his residence in Addis Ababa, the Ethiopian capital.
Many of those attempting the coup were arrested, including Gen Seare's bodyguard.
Mr Abiy said his government foiled the coup attempt in Amhara state, to the north of Addis Ababa, in a television address on Saturday night.
He said on Sunday that the situation ws now under "full control by the federal government".
Retired major general Gezai Abera was also killed.
Dr Mekonne and a regional government officer adviser, Ezez Wassie, were both killed in Amhara, while regional attorney general, Migbaru Kebede sustained heavy injuries.
The US State Department issued a travel warning, saying gunfire had been heard in Addis Ababa and advising personnel to find shelter.
A spokesman for UN Secretary General Antonio Guterres said he was "deeply concerned" by the weekend's events.
"Mr Guterres condemns the killing of the president of the Amhara National Region, the chief of staff of the Ethiopian National Defence Force and two other senior civilian and military staff," the spokesman said.
"He calls on all Ethiopian stakeholders to demonstrate restraint, prevent violence and avoid any action that could undermine the peace and stability of Ethiopia."
The spokesman said that Mr Guterres welcomed the commitment of Mr Abiy and government of Ethiopia to ensure that the perpetrators were brought to justice.
He said the UN remained committed to supporting Ethiopia in its efforts to address ongoing challenges.
Early on Sunday, Brig Gen Tefera Mamo, head of special forces in Amhara, told state television that "most of the people who attempted the coup have been arrested, although there are a few still at large".
Residents in Amhara's capital Bahir Dar said late on Saturday that there was gunfire in some neighbourhoods and some roads had been closed off.
Ethiopia has undergone a rapid period of reform under Mr Abiy, who within months of taking office normalised relations with Eritrea and its Horn of Africa neighbours, and reduced corruption.
Now Mr Abiy has gone from brokering peace between his country and Eritrea, to brokering peace between the military and civilians in Sudan.
His early efforts have appeared to be successful, with both sides agreeing to a civilian-led transition government, weeks after they vowed to cease communication.
Saturday's violence is not the first opposition Mr Abiy has survived. Shortly after his election in June last year, militants from the Oromo Liberation Front threw grenades at a rally attended by Mr Abiy, killing two.
He was forced to defuse tensions with a group of disgruntled soldiers in October last year by using his physical strength.
The group of soldiers were protesting against low pay and after listening to their concerns, Mr Abiy matched the soldiers push-up for push-up.