In Amhara, a northwestern state rocked by the murder of its president, attorney general and a top adviser, vast crowds gathered in a stadium in the local capital Bahir Dar for a funeral ceremony.

"The fallen will be remembered for generations to come for their contribution to the region and the whole country," said deputy prime minister Demeke Mekonnen, himself from the Amhara ethnic group, the second-largest in the country.

"We will find out the motives and interests of those who committed this barbaric act."

Demeke lay flowers before the three coffins, which were then to be taken to a local church for a religious service.

The authorities say the three were killed by a "hit squad" under the orders of Amhara security chief Asaminew Tsige, an ethno-nationalist reportedly facing removal over his attempts to form a militia.

- 'He did it for us' -

He is believed to have also co-ordinated the murder of the country's army chief Seare Mekonnen by his bodyguard in Addis Ababa.

Asaminew, who was shot dead by police on Monday, was also buried in Amhara, with witnesses describing crowds lining the roads to honour him in his birthplace Lalibela -- famed for its ancient rock-hewn churches.

A funeral ceremony attended by local officials and religious leaders was held in one of the churches, before the coffin was taken to a local cemetery.

"More than 1,000 people were at the burial ceremony," a tour guide in the region, Taye Abebe, 34, told AFP.

"The general public, including me, we don't believe what we are hearing on state television. We don't believe he did it, and if he did, he did it for us and the people," he said.

"One cannot say it is a coup, because there has never been a coup against a regional state, it has to be against the federal government. But if he really did that, he did it to protect the needs, the demands and the interests of the region."

Asaminew was only last year released from almost a decade 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 Ahmed.

- Unprecedented ethnic violence -

Meanwhile in Tigray region, which abuts Amhara to the north, slain army chief Seare Mekonnen was to be buried following the arrival of his coffin on Tuesday evening which also drew tens of thousands.

Seare was shot dead by his bodyguard while leading the response to the attacks in Amhara on Saturday.

The attacks were 500 kilometres (310 miles) apart but the government says they were coordinated.

Asaminew had persuaded Seare's bodyguard to kill him, it says. However, details have been scant.

Analysts say the killings highlight the scale of Ethiopia's political crisis.

Since taking office in April 2018, Abiy has been pushing through democratic reforms that have been lauded abroad but unleashed turbulence at home.

In a statement Tuesday, the International Crisis Group said the reforms had come at a cost, weakening the once all-powerful ruling EPRDF, a coalition of four regional parties that has ruled with an iron fist since 1991.

Security reforms have reduced the number of top officials from the Tigray People's Liberation Front (TPLF), representing the minority Tigray who had long dominated the party and were seen as marginalising the other major ethnic groups.

The changes have also led to a surge in ethno-nationalist parties in Ethiopia's nine autonomous regions, challenging the traditional parties ahead of elections planned for next year.

"The heightened ethno-nationalist rhetoric contributes to intercommunal violence, which over the past eighteen months has reached levels unprecedented in many decades in Ethiopia," the ICG said.

Over two million people have been displaced in violence along the borders of the regions, which divide the country along ethnic lines.

"The most pressing threat is that the 22 June killings could trigger intensified power struggles and violent reactions in politically sensitive locations across the country," said the ICG.