DAKAR, Senegal — The Democratic Republic of Congo and Rwanda-backed rebels have signed a declaration of principles for a permanent ceasefire in eastern Congo, where ethnic tensions and a quest for rich minerals have resulted in one of Africa’s longest conflicts, with thousands killed this year alone.

Congo and Rwanda-backed rebels on Saturday signed a declaration of principles in Qatar to end decadeslong fighting in eastern Congo that commits them to a permanent ceasefire and a comprehensive peace agreement to be signed in one month.