The authorities detained Agaw Democratic Party leader Andualem Tilahun and another senior party member, Beyilu Teshale, on August 29, but the information was only made public on Monday.
The party represents the Agaw people, an ethnic group numbering around two million based in the northern Amhara region, who have largely kept out of the trouble that has flared in Ethiopia this year.
“Andualem Tilahun was charged on allegedly public incitation against the government, which is not true,” Tesera Be, a party advisor who is currently in the United States, said.
“The charge is politically motivated to eliminate the opposition party in the region.”
The spokesperson for the regional government could not be reached for comment.
Ethiopia – regarded as among Africa’s most repressive states – has been hit by anti-government protests, starting in the central Oromo region in November last year and spreading in July to Amhara.
The government has cracked down hard on the dissent, and Human Rights Watch estimates that more than 400 people involved in the protests have been killed by security forces since November.
Be insisted the party officials were “never involved in any incitement to demonstrate against the government”, adding: “Their only objective is to obtain a regional state for the Agaw, like the Oromo or the Amhara.”
A few days before his arrest Tilahun was contacted by AFP to confirm that security forces were going from house to house in his village to persuade people not to take part in anti-government demonstrations.