Ethiopia's army chief was shot dead by his bodyguard just hours after an attempted coup in Amhara state left the regional president and another top adviser dead, a spokeswoman for the prime minister said on Sunday.

The spokeswoman Billene Seyoum told journalists a “hit squad” led by Amhara's security chief Asaminew Tsige burst into a meeting on Saturday afternoon, injuring regional president Ambachew Mekonnen and another top official who both died of their wounds.

Later that evening in what appeared a “co-ordinated attack”, army chief Seare Mekonnen, and a retired general who was visiting him, were killed by his bodyguard, said Billene.

The bodyguard has been apprehended while Asaminew is still on the loose, sources said. Analysts said the incident showed the seriousness of the political crisis in Ethiopia, where efforts by Abiy to loosen the iron-fisted grip of his predecessors and push through reforms has unleashed a wave of unrest.

“These tragic incidents unfortunately demonstrate the depth of Ethiopia's political crisis,” said International Crisis Group analyst William Davison.

“It is now critical that actors across the country do not worsen the instability by reacting violently or trying to exploit this unfolding situation for their own political ends,” the expert said.

Earlier on Saturday, Prime Minister Abiy Ahmed said that the army chief was shot while trying to thwart an attempted coup on Saturday in a federal state north of the capital Addis Ababa.

Speaking on state television, Abiy said General Seare Mekonnen was one of several casualties.

“He was shot by people who are close to him,” Abiy said.

Read more: Ethiopian PM escapes rally grenade attack that kills one, wounds scores

The prime minister said the general had been trying to prevent plotters carrying out a coup in Amhara state, one of Ethiopia's nine federal states.

Since coming to power last year, Abiy has tried to spearhead political reforms, to open up the once isolated, security-obsessed country of 100 million people on the Horn of Africa.

Abiy has released political prisoners, removed bans on political parties and prosecuted officials accused of gross human rights abuses, but his government is battling mounting violence.

Ethnic bloodshed — long held in check by the state's iron grip — has flared up in many areas, including Amhara, where the regional government was led by Ambachew Mekonnen.

According to Abiy, regional government officials were in a meeting when a coup attempt occurred. “There are a few people who were killed while others were injured,” Abiy said.

A regional television broadcaster affiliated with the Tigray People's Liberation Front (TPLF), a member of Abiy's coalition, reported Seare had been killed, alongside another senior military official, Gize Abera.

The US Embassy said on Saturday that it was aware of reports of gunfire in Addis Ababa, though Reuters could not confirm those reports.

“Chief of Mission personnel are advised to shelter in place,” the Embassy said on its website.

Later on Sunday, Brigadier General Tefera Mamo, the 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 there was gunfire in some neighbourhoods and some roads had been closed off.

Ethiopia is due to hold a national parliamentary election next year. Several opposition groups have called for the polls to be held on time despite the unrest and displacement.