Ethiopia's government urged Tigrayan rebels to join a unilateral ceasefire in their conflict on Thursday as aid agencies struggled to reach hundreds of thousands of people facing famine.

The UN on Friday urged the rebel Tigray Defense Forces group to "immediately and completely" endorse the ceasefire that the Ethiopian government has announced in the war-hit region.

The United Nations said on Friday conflict could rapidly flare again in Ethiopia's Tigray and that famine was worsening in the region, where local fighters declared victory this week after an eight-month war with central government and allied forces.

Ottawa is calling on Eritrea to withdraw its armed forces from the Tigray region in Ethiopia, a couple days after a ceasefire was announced to put a hold on a conflict that has led to one of the world's worst famine crises.  

The crisis has killed thousands of civilians, with hundreds of thousands facing the world's worst famine crisis in a decade.

The ceasefire declaration came after rebel fighters recaptured Mekelle, the capital of the restive Tigray province.