Fifty two individuals were killed and a lot more injured during a protest at a religious festival in the Oromia area of Ethiopia, the government says.
Some died in a stampede after police employed tear gas, rubber bullets and baton charges, witnesses said.
Prime Minister Hailemariam Desalegn said rioters had caused “pre-planned mayhem” that led people to fall to their deaths in ravines.
He denied reports the security forces had opened fire.
In a national address on state TV, he praised their “great efforts” to shield the people and blamed “bad forces” for the deaths, vowing to bring to justice those responsible..
Thousands had gathered for the religious festival in Bishoftu, 40km (25 miles) in the capital Addis Ababa.
Some reports said police reacted after anti-government protesters threw stones and bottles, but others said demonstrators were totally peaceful.
Jawar Mohamed, an Oromo activist, was quoted as saying that almost 300 people had been killed and many more injured.
There continues to be a string of deadly battles in Ethiopia in recent months.
People in the Oromia and Amhara regions have whined about political and economic marginalisation.
The US has expressed anxiety about what it termed the excessive use of force.
Bunches at Sunday’s Oromo festival, which AP news agency said had attracted two million individuals, chanted “We desire liberty” and “We need justice”, witnesses said.
Some participants crossed their wrists above their heads, a gesture that is becoming a symbol of Oromo protests.
The unrest was triggered last November by a plan to expand the capital. This led to fears that the biggest in Ethiopia, farmers from the Oromo ethnic group, would be displaced.
The plan was later dropped but protests continued, highlighting problems such as human rights and marginalisation.