A senior US official has said for the first time that a “humanitarian crisis” is unfolding in Ethiopia’s Ogaden region, putting Washington at odds with the Addis Ababa government, which has rejected similar claims from aid organisations.

Jendayi Frazer, assistant secretary of state for African affairs, made the comment on Saturday following a trip to the region, where government forces are fighting rebels who this year stepped up a violent campaign for self-determination.