The internet has been shut down since Sunday.

Eskinder Nega, a prominent rights activist, said that several members of his Baladera Council group have been detained in a wave of arrests by the security forces since Saturday's killings.

Widespread arrests are taking place in Bahir Dar, the regional capital of Amhara, according to residents, who spoke on condition of anonymity for their security.

Abiy's visible distress at the service is understandable, according to experts on Ethiopia's politics.

"The assassinations were a severe setback to Abiy and a wake-up call showing the fragility of his reform plans," said Alex Vines, head of the Africa Program at Chatham House in London.

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"Abiy has shown tremendous bravery in his reform agenda and in trying to dismantle the military and security regime that had run Ethiopia. These attacks show that some of those threatened by his reforms are striking back. The danger is that Abiy will respond to this by becoming more authoritarian himself."

The weekend assassinations in Addis Ababa and Amhara were "a blow to Abiy's democratisation agenda and may well worsen Ethiopia's political and security crisis if key issues are not urgently tackled", said William Davison, senior analyst on Ethiopia for the International Crisis Group.

"Abiy's challenges include divisions within the ruling EPRDF party that are exacerbated by opposition challengers, including strong ethno-nationalist movements," said Davison. "The consequent dysfunction of an until recently all-powerful ruling coalition is reducing government effectiveness and contributing to the insecurity.