The United Nations World Food Programme (WFP) has said it is temporarily suspending food aid to Ethiopia because its supplies are being diverted.

The announcement came a day after the United States Agency for International Development said it was doing the same.

“Food diversion is absolutely unacceptable, and we welcome the government of Ethiopia’s commitment to investigate and hold accountable those responsible,” WFP executive director Cindy McCain said.

Some 20 million Ethiopians rely on food aid because of drought and conflict, out of the country’s population of roughly 120 million. Much of the aid comes from USAID and the WFP.

The suspensions have brought worries that malnutrition could rise in Africa’s second most populous country.

USAID, WFP and the Ethiopian government have not said who is responsible for the food diversion, which the US has described as “widespread and coordinated”.

However, an internal memo prepared by a group of foreign donor representatives and seen by the AP this week pointed at government involvement.

“The scheme appears to be orchestrated by federal and regional government of Ethiopia entities, with military units across the country benefiting from humanitarian assistance,” said the document from the Humanitarian and Resilience Donor Group, which includes bilateral and multilateral partners.

In a joint statement with USAID on Thursday, the Ethiopian foreign ministry spoke of “deeply concerning revelations” and said it was investigating with the US “so that the perpetrators of such diversion are held to account”.

The nationwide food aid suspensions follow USAID and WFP saying last month they had suspended food deliveries to Ethiopia’s northern Tigray region while they investigated reports of food aid theft there. The region is recovering from a two-year conflict.

That suspension by the WFP and allegations of aid diversion in Tigray were first reported by the AP. Some 5.4 million of the region’s six million people rely on humanitarian help.

Earlier this year, USAID administrator Samantha Power told the Senate Foreign Relations Committee that aid theft in Tigray appeared to “involve collusion between parties on both sides” of the conflict, which ended in November.

In its statement on Friday, WFP said it was continuing other programmes in Ethiopia for children, mothers and drought-hit farmers.

“WFP is working closely with its UN and humanitarian partners and local stakeholders to reform the way assistance is delivered across Ethiopia and in all high-risk operational contexts where we work,” it said.