Lobby group Human Rights Watch has accused the Ethiopian government of violently suppressing protests, after disputed elections last year.
Clashes between police and protesters followed last year's polls
The group said investigators in rural areas in the Oromia and Amhara regions had reported intimidation, excessive force and arbitrary detention.
HRW also said officials had withheld seed and fertiliser from farmers suspected of supporting the opposition.
The government has blamed its opponents for recent unrest and violence.
The group says federal police have been responsible for many abuses.
"The Ethiopian government is violently suppressing any form of protest and punishing suspected opposition supporters," Peter Takirambudde, director of HRW's Africa Division, said in a press statement.
"Donor governments should insist on an independent, credible investigation into abuses by federal police and local officials in rural as well as urban areas."
May's election was the most closely contested in Ethiopian history, and resulted in the opposition winning more than 100 seats in parliament.
But the opposition believed they had been cheated of victory, and took to the streets.
The clashes left many dead, and Prime Minister Meles Zenawi accused the opposition of attempting to overthrow his government.
"The government is deepening its crackdown in Ethiopia's rural areas, far from the eyes and ears of international observers in Addis Ababa," Mr Takirambudde said.
Late last year, Western donors threatened to withhold $375m in direct aid to the Ethiopian government, as 80 journalists and opposition leaders appeared in court.