Cholera and measles outbreaks have been recorded in Amhara and Afar, where aid agencies have limited access.

In Tigray, where there has been no air or road access for eight weeks, the WHO is unable to get a clear picture of disease outbreaks.

However officials say childhood vaccinations have stopped and that supplies of IV fluids, insulin and antibiotics have run out. Fewer than one in 10 health centres are functioning.

There are acute shortages of food and fuel, with an estimated 89% of the population in Tigray now food insecure, and 29% of children suffering malnutrition.

Across Tigray, Amhara and Afar, the UN estimates that 13 million people need humanitarian assistance.

Earlier this month, the head of the WHO, Dr Tedros Adhanom Ghebreyesus, who is from Tigray, said there was "a very narrow window to prevent genocide".

On Friday, WHO officials would not be drawn on these comments, but repeated that access to Tigray was a matter of urgency.

Peace talks between the Ethiopian government and Tigrayan representatives began in South Africa this week, but have not led so far to any increased access for humanitarian organisations.