A deadly stampede broke out after Ethiopian police reportedly fired tear gas to break up an ethnic Oromo protest during a festival with several people killed south of the capital, Addis Ababa.
There were conflicting death toll reports following the stampede in Bishoftu on Sunday. An AFP photographer at the scene said he saw 15-20 unmoving bodies, some of whom were clearly dead.
And Associated Press report said "several dozens" have died.
"As a result of the chaos, lives were lost and several of the injured were taken to hospital," the government communications office said in a statement, without giving exact figures. "Those responsible will face justice."
An estimated two million people were attending the annual Irrecha event in Bishoftu town, 40km southeast of the capital. The event took place in one of the country's most sensitive regions, Oromia, which has seen several months of sometimes deadly protests demanding wider freedoms.
Merera Gudina, chairperson of the opposition Oromo Federalist Congress, told Reuters news agency at least 50 people were killed when people fled after police fired tear gas and shots in the air to disperse anti-government protesters at a crowded religious festival.
The government and opposition often give different accounts for casualties during protests.
Crowds chanted "we need freedom" and "we need justice" and prevented community elders, deemed close to the government, from delivering their speeches at a religious festival, prompting police to fire tear gas that caused the stampede.
Protesters chanted slogans against the Oromo People's Democratic Organisation, one of four regional parties that make up the Ethiopian Peoples' Revolutionary Democratic Front, which has ruled the nation for quarter of a century.
Sporadic protests have erupted in Oromia region in the last two years, initially sparked by a land row and increasingly turning more broadly against the government.
According to New York-based Human Rights Watch, at least 500 people have been killed by security forces since the demonstrations began in November. Though protests started among the Oromo - Ethiopia's biggest ethnic group - they later spread to the Amhara, the second-most largest in the country.
Both groups say the ruling coalition is dominated by the Tigray ethnic group, which makes up only about six percent of the population.
What is triggering Ethiopia's unrest?
Small protests in Oromia province initially flared in 2014 over a development plan for the capital that would have expanded its boundaries, a move seen as threatening the seizure of farmland.
The government has blamed rebel groups and dissidents abroad for stirring up the protests and provoking violence.
The government has denied that violence from the security forces is systemic, though a spokesman has previously told Al Jazeera that police officers "sometimes take the law into their own hands", pledging an independent investigation.
The Ethiopian People's Revolutionary Democratic Front last month rejected a United Nations request to send in observers, saying it alone was responsible for the security of its citizens.