The government's response is said to be "a very dangerous escalation of this volatile situation"
At least 75 protesters have been killed during weeks of demonstrations in Ethiopia, according to the Human Rights Watch group.
Police and soldiers are reported to have used lethal force amid continued tension between demonstrators and security forces.
The country's Anti-Terrorism Task Force is now leading the government's response to the situation, with officials saying the protesters are planning to "destabilize the country”.
While Ethiopian authorities have said five demonstrators and an undisclosed number of security force members have been killed, HRW says the number is likely much higher.
Leslie Lefkow, deputy Africa director at Human Rights Watch, said, “the Ethiopian government’s response to the Oromia protests has resulted in scores dead and a rapidly rising risk of greater bloodshed.
"The government’s labelling of largely peaceful protesters as ‘terrorists’ and deploying military forces is a very dangerous escalation of this volatile situation," she added.
The protests began in the small town of Ginchi, around 80 kilometers southwest of the country's capital Addis Ababa. The demonstrations were sparked when authorities sought to clear a forest for an investment project.
The protests later spread to other areas of the Oromia region - home to an estimated 35 million Oromo, the country's largest ethnic group. Further large scale demonstrations were held in opposition to the proposed expansion of the Addis Ababa municipal boundary.
Amnesty International has also denounced the government's response to the demonstrations, with Muthoni Wanyeki of the organisation's East Africa division stating “the government should desist from using draconian anti-terrorism measures to quell protests and instead protect its citizen’s right to freedom of expression and peaceful assembly".