The Sudan People's Liberation Movement-North (SPLM-N) said that 20% of families were suffering severe food shortages, while 30% of children suffered from malnutrition. An Arabic version of the statement described the situation as a famine.
It said the parties involved in Sudan's civil war and a poor harvest were to blame for the crisis.
The situation in the two regions was "the most severe compared to other states," the SPLM-N said. "The little foodstock that the host community has been able to produce is being shared and rapidly depleted."
Some 3.9 million people live in the two territories under SPLM-N control, a number that swelled after people from other parts of the country were displaced by the fighting.
The ongoing war between Sudan's army and the paramilitary Rapid Support Forces (RSF) has plunged half the population of about 50 million into food insecurity and created the world's largest humanitarian crisis.
Across the country, some 756 000 people face catastrophic hunger, the Integrated Food Security Phase Classification, a global hunger monitor, said in June.
Both the army and the RSF are accused of blocking aid from reaching targeted areas, and of damaging the infrastructure and markets needed for food production and delivery.
The SPLM-N accused the army-aligned government in Port Sudan of selling aid allocated for the area, while it said the RSF was closing markets.
"Civilian villages in both regions were also targeted through a scorched earth policy, burning crops and homes, displacing residents to camps, and blocking roads," it said.
The army and RSF did not immediately respond to requests for comment.
--Reuters--