The Ethiopian prime minister, Abiy Ahmed, was recently awarded the Nobel Peace Prize for helping to end Ethiopia’s 20-year war with Eritrea. Photograph: Mikhail Metzel/Sputnik/Kremlin Pool/EPA

Violence in Ethiopia that began with protests against the prime minister, Abiy Ahmed, and quickly morphed into ethnic clashes has left 67 people dead in Oromia state, a police official said on Friday.

“The total number dead in Oromia is 67,” said Kefyalew Tefera, the regional police chief, adding that five of the dead were police officers.

The spike in the death toll came as the high-profile activist at the centre of the violence accused Abiy, this year’s Nobel peace prize laureate, of acting like a dictator and suggesting that he might challenge him in elections planned for next year.

Violence erupted in the capital, Addis Ababa, and in much of Ethiopia’s Oromia region on Wednesday after the activist, Jawar Mohammed, accused security forces of trying to orchestrate an attack against him – a claim police officials denied.

Kefyalew told AFP that the violence had ended in Oromia, but the Amnesty International researcher Fisseha Tekle said on Friday that he was still receiving reports of attacks.

The defence ministry said that it was deploying forces to seven hotspots to restore order, according to the state-affiliated Fana Broadcasting Corporate.

Jawar is credited with promoting protests that swept Abiy to power last year but he has recently become critical of some of the premier’s policies.

In an interview at his residence in Addis Ababa, Jawar told AFP that Abiy seemed to be taking Ethiopia back to “the old ways” of authoritarian rule.

“He has resorted to the early signs of dictatorship, of trying to intimidate people, even his very close allies who helped him come to power who happen to disagree with some of the policies and positions and ideologies he’s advocating,” Jawar said. “Intimidation is the start of authoritarian rule.”

Both men are members of the Oromo ethnic group, the largest in Ethiopia.

Their feud highlights divisions within Abiy’s Oromo support base that could complicate his bid for a five-year term when Ethiopia votes in elections, currently planned for May 2020.

Jawar said that running against Abiy was “one possibility”, though he also said he could be convinced to back the prime minister if he changes course.

“I want to have an active role in the coming election. In what capacity I’m not sure but I want to make sure that the influence I have in the country has a positive contribution,” he said.

After two days of violent protests, tensions had cooled on Friday in Addis Ababa, although the total damage inflicted by the unrest was still being tallied.

Fisseha said the violence had included instances of security forces opening fire on protesters, but that it was increasingly taking the form of ethnic and religious clashes.

“Some people have lost their lives with sticks, with machetes, some houses have been burned. People have been using even bullets and light arms to kill each other, to fight each other,” he said.

At least six people were killed in the town of Ambo, west of Addis, after security forces opened fire on protesters, Fisseha said. Ethnic and religious violence has been reported in the towns and cities of Dodola, Harar, Bale Robe and Adama.