Dozens of people were killed in fighting during a foiled coup by a rogue state militia in Ethiopia's Amhara region at the weekend, the regional government spokesperson said on Wednesday, the first official report of significant clashes.

The militia attacked the police headquarters, ruling party headquarters and president's office, where they executed three top officials, in Amhara's regional capital of Bahir Dar on Saturday, Asemahagh Aseres told Reuters on the sidelines of a state burial for the officials who were killed.

The militia was a recently formed unit of the region's security services. Its appealing for others to join its take-over were rebuffed, Asemahagh said.

"They are part of our police. They are not independent," he told Reuters. "(But) most of the forces were not with them. They defended (us) very well."

The fact that the militia were state forces rather than independent raises the stakes for the government of Prime Minister Abiy Ahmed, who has rolled out a package of economic and political reforms since taking office in April last year.

He has lifted a ban on political parties, released journalists, rebels and prisoners, and prosecuted officials accused of abuses. But his shake-up of the military and intelligence services has earned him powerful enemies.

The spokesperson said the militia had detained him when it took over a guesthouse for government officials and also tried and failed to take over the region's state media. He said the militia were then chased out of the city.

A journalist confirmed to Reuters that militia members had approached, but withdrawn without firing at the media building's armed security. Regional state-run media has reported 13 deaths in the violence so far.

Reuters could not independently verify Asemahagh's death toll, but two independent witnesses Reuters interviewed in a coffeehouse the night before confirmed the militia attacked the three targets he named.

Details of more deaths in a separate but possibly linked attack in a neighboring state also emerged on Wednesday.

Men in camouflage uniforms killed more than 50 people and injured 23 others in the Metakal zone of the Benishangul-Gumuz region early on Monday, the region's peace and security bureau head Abera Bayeta said.

"We are still investigating but we have our suspicion that those attackers might be the same people who were involved in the coup in Amhara region," he said.

The government has accused Amhara's former security chief of masterminding the twin attacks that killed the region's president Ambachew Mekonnen, two other officials in Bahir Dar, the Chief of Staff and another general 325 kilometers away in the national capital Addis Ababa the same night.

Alleged coup mastermind Asamnew Tsige, who was shot dead by security forces on Monday, was accused of trying to seize control of Amhara, not the whole country.

Thousands lined the streets in Ethiopia's two main northern cities on Wednesday in mourning. In Bahir Dar, capital of Amhara, priests from Ethiopia's Orthodox Church gave sermons calling for forgiveness as the bodies of officials were laid out at the presidential house.

Three flower-covered black hearses carrying the state president, his adviser and the state's attorney general wound their way through the streets accompanied by traditional flute music before being buried with military salutes.