The Nobel prize awarded last week to Ethiopia’s prime minister, Dr Abiy Ahmed, honoured his achievements as a peacemaker. Most widely recognised was his success in thawing relations with Eritrea, the breakaway republic with which Ethiopia had remained on a war footing since the country gained independence in 1993.

No less significant, however, was his management of the internal conflict between the Ethiopian government and protesters in Oromia, the region surrounding Addis Ababa, the capital. Rather than attempting to shut down the protests by force, Abiy acknowledged their grievances, and opened up political space. He freed political prisoners jailed by previous administrations, and restored the legitimacy of parties formerly branded as terrorist organisations.

Almost single-handedly, Abiy appeared to have restored people’s faith in their political institutions. Not only in Addis, but in provincial towns, administrative posts and truck stops across the country, posters and T-shirts bearing his image were proudly displayed, often accompanied by the Amharic word andinet, meaning “unity”. After an assassination attempt in June last year, he impressed by pleading for forgiveness and brotherhood.

Among those who saw new hope for the future were members of the country’s pastoralist groups, who had long been accorded a marginal place in Ethiopia – both literally and figuratively – including Somalis, Oromos and many others in the country’s far north, east, south and west. For the first time in their lives, many felt they could have a government that fostered respect among all citizens.

“Abiymania” would soon be shaken, however, as new conflicts reared their heads. The system of ethnic federalism, devised as a way of uniting a diverse coalition of peoples who had fought against the regime of Mengistu Haile Mariam, had succeeded in bringing people together, but at a cost. Those who found themselves on the wrong side of an ethnically defined border, such as the Gedeo in Oromia, were subject to a new wave of persecution. The resulting conflicts left more people internally displaced than in any other country.

If these events received less international coverage than they deserved, others of equal gravity have gone almost entirely unreported. In the past month, government forces have carried out indiscriminate killings in the Lower Omo region. Multiple reports, from independent sources, suggest that among the Bodi ethnic group at least 38 people – including women, children and the elderly – were shot or beaten to death by the military. Women were gang raped. Scores more have disappeared or are in hiding.

Among the neighbouring Mursi people, a similar process appears to be underway, with reports of houses set on fire, beatings and treatment that amounts to torture: soldiers forcing people to sit all day in the equatorial sun, and denying men and women the simple dignity of privacy for urinating and defecating.

South Omo, where these abuses are occurring, is a site of major infrastructure investments by the Ethiopian state and corporate partners. In 2016 the Gibe III dam was inaugurated upstream. By reducing the river’s natural flood, it allowed large sugar plantations to be established alongside the river, connected to the regional centres by an expanding network of roads.

The Bodi and their neighbours were not consulted before these projects began, and lost their lands and livelihoods as plantations, roads and camps for migrant workers were established. The campaign of violence to which the military are now subjecting them threatens to destroy their social fabric entirely.

Regardless of who issued the orders, the peace prize bestowed on Ethiopia’s prime minister is a call to halt these atrocities. When Abiy assumed power, it was by riding a wave of discontent over the displacement of poor farming communities around Addis Ababa, whose grievances he – uniquely among senior politicians in the country – had the courage to acknowledge. Whereas the displacement of communities in the vicinity of the capital sparked outrage, the unjust treatment of ethnic minorities has not, so far, attained the status of a popular issue.

For the people of the Lower Omo, the situation is desperate. But for Ethiopia and its friends, there is still a chance of salvage. Working for peace, as Abiy well knows, inspires most when it is carried out not in good times – when people are already united – but when power appears to reside with the forces of violence and division.

When Dr Martin Luther King accepted the Nobel peace prize in 1964, he spoke of leaving Oslo “inspired with renewed dedication to humanity”. We hope that, like King, Abiy will interpret the prize not as a capstone to his efforts, but as a commission to work harder than ever for peace and justice. By championing the cause of those on the margins, he would be fulfilling the highest duty of a statesman.

• Jed Stevenson is an assistant professor of anthropology at Durham University in the UK. Felix Girke is a postdoctoral researcher at Konstanz University in Germany