Thousands of people have been arrested across Ethiopia following violent clashes in which police killed 36 people, a U.S.-based human rights group reported Wednesday.
Human Rights Watch said student activists and opposition supporters had been rounded up in a crackdown after last week's fighting.
"Opposition rhetoric may well have contributed to last week's unrest, but the government must take responsibility for the conduct of its own security forces," said Georgette Gagnon, the deputy director of the New York-based group's Africa division. "The security forces have killed dozens of protesters and arbitrarily detained thousands."
Ethiopian federal police said some detainees were being held at Ziway detention facility, 90 miles south of the capital.
Arrests continued in the capital, where police this week detained at least three members of the Ethiopian Human Rights Council. Human Rights Watch said it had obtained reports of mass arrests in at least nine cities.
"Opposition members and students in other cities are increasingly at risk of arbitrary arrest and torture," Gagnon said. Many of those arrested in earlier roundups had been released, but smaller-scale arrests continued, she said.
Ethiopia's main opposition leader, Hailu Shawel, was freed from house arrest Tuesday after two days of talks mediated by the European Union. The country's main political parties agreed to work for peace after 10 days of unrest.
Ethiopia's ruling party, which has pledged itself to democratic reform but has shown authoritarian tendencies, claimed victory in last month's parliamentary elections, but parties have lodged complaints in 299 of the 527 voting districts. The violence that followed threatens to destabilize Ethiopia, one of the poorest countries in the world.
In Washington, the State Department called on the Ethiopian security forces Tuesday to avoid use of excessive force in dealing with post-election violence.