Ethiopia has arrested thousands of members of the Oromo ethnic group over the past three months, according to Amnesty International.
The London-based human rights group said students were among those who have been rounded up since November.
Amnesty said the arrests follow protest calls by the rebel Oromo Liberation Front against alleged government fraud.
..."Those detained have reportedly been accused of links with the OLF, although none of them has yet been charged," it said.
It called on Ethiopian authorities to either charge or release the detainees and investigate alleged mistreatment of some of those held.
Meanwhile, the US-based Committee to Protect Journalists (CPJ) said Frezer Negash, an online journalist for the Ethiopian Review, had been arrested on Friday and was being held without charge in Addis Ababa.
'Thousands arrested' in Ethiopia (BBC News) February 1, 2006