Since April 2023 the federal government has been locked in conflict with the Fano, a long-standing "self-defence" militia for the Amhara ethnic group, Ethiopia's second largest.

In September, the federal army deployed large numbers of troops across the region together with the Amhara security authorities.

Since September 28, this task force "has filled four makeshift detention camps across the Amhara region with thousands of civilians", Amnesty said.

The rights group said it had interviewed two people recently released from the detention camps, five family members of detainees and nine reliable sources with knowledge of the mass detentions.

A former detainee said local police "broke into my home with a rifle, arrested me in front of my children, and gave no explanation. I was helpless".

A number of sources also told Amnesty the Ethiopian authorities were organising what they call "rehabilitative training" in these camps.

As the authorities have restricted access to the region the claims could not be independently verified.

Amnesty said Ethiopia "must end the month-long arbitrary mass detention of thousands in the Amhara region".

The wave of arrests has also targeted those who challenged the government's interference in the judicial system, as well as a large number of academics.

"Ethiopia has entered a new era of disregard for national, regional and international human rights obligations," said the group's regional director for East and Southern Africa, Tigere Chagutah.

"Over the past five years, arbitrary mass detentions have been used as political tools to silence peaceful dissent, often under the guise of sweeping state of emergency laws," Chagutah said.

Ethiopia declared a state of emergency in the northern Amhara region, home to around 23 million people, in August 2023.

While this expired in June 2024, turmoil has continued to plague the restive region.

The conflict was triggered by the federal government's attempts to disarm the Fano.