Addis Ababa - An Ethiopian rights group on Monday accused government forces of more than 100 extra-judicial killings as well as torture while putting down protests that began last year in the Oromia region.

The Human Rights Council (HRC) of Ethiopia, a non-governmental organisation, said security forces had committed "criminal acts" between November 2015 and last month when the protests ended.

"Most of the victims were shot in the back or in the head," the group said in a report, after identifying "102 extra-judicial killings" of people ranging in age from 12 years to 68.

A further 56 people were either shot or beaten and 22 were tortured, according to the report.

With 27 million inhabitants, the Oromia region encircles the capital Addis Ababa and has its own Oromo language.

The demonstrations began in November against a government plan to expand the boundaries of Addis Ababa into Oromia. The plan was dropped on January 12 but protests continued for weeks more.

"Many of the killings occurred at night, after protests, while people were walking in the streets," said Kumlachew Dagne, HRC's vice chairman.

"Government armed men are conducting house-to-house searches at night, committing illegal acts of beating, threats, intimidation and harassment," the report said, adding that "cases of rape by members of government armed forces" were also recorded.

The group said it was unable to give a estimate of the how many people died in total during the months of unrest, but advocacy organisation Human Rights Watch has estimated that at least 140 were killed.

Last week Ethiopian Prime Minister Hailemariam Desalegn reportedly apologised for the deaths telling parliament that "anti-peace forces" were behind the protests but that "legitimate questions" must be heard.

Hailemariam added that his government, "unreservedly apologises to our people for what happened."