Fifty-two people died in a stampede at a religious festival in Ethiopia to celebrate the end of the rainy season, the regional government said.
Violence broke out at the gathering in the town of Bishoftu near the capital Addis Ababa due to the actions of "irresponsible forces", the authorities said in a statement, adding that "as a consequence, 52 people died in this crush."
Sporadic protests have erupted in Oromiya in the last two years, initially sparked by a land row but increasingly turning more broadly against the government. Since late 2015, scores of protesters have been killed in clashes with police.
These developments highlight tensions in the country where the government has delivered stellar economic growth rates but faced criticism from opponents and rights group that it has trampled on political freedoms.
Thousands of people had gathered for the annual Irreecha festival of thanksgiving in the town of Bishoftu.
Crowds chanted "we need freedom" and "we need justice", preventing community elders, deemed close to the government, from delivering their speeches at the festival.
Some protesters waved the red, green and yellow flag of the Oromo Liberation Front, a rebel group branded a "terrorist" organisation by the government, witnesses said.
When police fired teargas and guns into the air, crowds fled and created a stampede, some of them plunging into a deep ditch, witnesses said.
The witnesses said they saw people dragging out a dozen or more victims, showing no obvious sign of life. Half a dozen people, motionless, were also seen being taken by a pick-up truck to a hospital, one witness said.
Merera Gudina, chairman of the opposition Oromo Federalist Congress, said at least 50 people were killed, saying his group had been talking to families of the victims.
He said the government tried to use the event to show Oromiya was calm. "But residents still protested," he said.
The government blamed rebel groups and dissidents abroad for stirring up the protests and provoking violence. It dismissed charges that it clamps down on free speech or its opponents.