However, a witness told the BBC that 47 were killed by the security forces.
The government did not say how most of the deaths had been caused but the Ambo resident said she had seen the army firing live ammunition
“I saw more than 20 bodies on the streets,” she said.
“I am hiding in my house because I am scared.”
The Ambo resident said that four students had been killed on Monday and another 43 in a huge security crackdown on Tuesday, after a huge demonstration including many non-students.
Since then, the town’s streets have been deserted, she said, with banks and shops closed and no transport.
She said teaching had been suspended at Ambo University, where the protests began, and students prevented from leaving.
In a statement, the government said eight people had died during violent protests led by “anti-peace forces” in the towns of Ambo and Tokeekutayu, as well as Meda Welabu University, also in Oromia state.
It said one person had been killed “in a related development” when a hand grenade was thrown at students watching a football match.
The statement blamed the protests on “baseless rumours” being spread about the “integrated development master plan” for the capital.
BBC Ethiopia analyst Hewete Haileselassie says some ethnic Oromos feel the government is dominated by members of the Tigre and Amhara communities and they would be loath to see the size of “their” territory diminish with the expansion of Addis Ababa, which is claimed by both Oromos and Amharas.
The student protestors are from Ethiopia’s biggest ethnic group, the Oromo, numbering around 27 million people.
Oromia is the country’s largest region, completely surrounding the capital Addis Ababa, although the city is itself part of the Amhara region.
Its people speak their own language – Oromifa – and see themselves as very different from the Amhara.
The protesters believe they face losing their regional and cultural identity if plans to extend Addis Ababa’s administrative control into parts of Oromia get the go-ahead.
Some have also raised fears of the potential for land grabs.
The so called “master-plan” for Addis Ababa is currently out for public consultation and the government says people are being given opportunities to raise their concerns.
Officials say the plan has been well publicised and will bring city services to poor rural areas.
The protestors claim they merely wanted to raise questions about the plan – but were answered with violence and intimidation.