UNICEF spokesman James Elder told reporters in Geneva that without humanitarian access to scale up response, estimated 30,000-plus severely malnourished children in those highly inaccessible areas are at high risk of death.
James Elder comments came after the UN said some 350,000 people in Tigray were facing famine, while two million more people were just a step away from those extreme conditions.
UN humanitarian chief Mark Lowcock said, warning that every expert you speak to will tell you this is going to get a lot worse. He added that fresh data showed the number of people classified as being in famine conditions was "higher than anywhere in the world at any moment since a quarter of a million Somalis lost their lives in 2011".
The UN has said that more than 90 percent of the more than five million people in the Tigray region need emergency food aid, and has urgently appealed for more than $200 million to scale up its response.
The United States and the European Union issued a plea for greater international efforts to tackle the emerging famine. International aid organisations have complained repeatedly that they are being denied access to the region by Ethiopian forces and troops from neighbouring Eritrea.