NAIROBI, Kenya — The prime minister of Ethiopia on Wednesday announced that the government would close a notorious detention center and release some prisoners across the country, including some members of political parties.

The announcement was hailed by human rights groups as an amnesty for the country’s political prisoners, who are estimated to number in the thousands, even though Hailemariam Desalegn, the prime minister, did not explicitly mention political prisoners in his address.

Some wondered exactly whom the prime minister intended to release.

“It was absolutely not clear what the prime minister was saying,” said Yacob Hailemariam, a lawyer in Addis Ababa, the capital. “The whole thing is filled with vague statements and vague promises. He was very equivocal, and we will have to wait to see what he really meant.”

The government of Ethiopia — Africa’s second most populous country and an important United States ally in the fight against terrorism — has never acknowledged that it holds political prisoners, which would violate the country’s Constitution.