WASHINGTON —  The United States is banning arms sales to Eritrea over concerns that it is aiding terrorists in the Horn of Africa.

U.S. officials have accused Eritrea of supporting terrorist groups tied to the Islamist opposition in Somalia.

Ethiopia, with U.S. backing, helped oust the Islamist government in 2006. Thousands have been killed in fighting between the government and opposition since then.

Members of the Islamist opposition are now operating in exile from Eritrea and gaining influence in Somalia.

The leader of the opposition, Sheik Hassan Dahir Aweys, is designated a terrorist under a U.N. Security Council resolution.

The United States announced the arms ban Monday in a government notice.