The United Nations is warning that two states in Sudan face a looming food crisis because of fighting between government troops and the party of former rebels.

The U.N. Food and Agriculture Organization on Wednesday called for “urgent action” in Blue Nile and Southern Kordofan states, both located along the border with newly-independent South Sudan.

The FAO said food availability in those states has been significantly reduced due to ongoing violence between the Sudanese army and members of the Sudan People's Liberation Movement-North .

The group is the northern branch of the organization that fought Khartoum during Sudan's long civil war and is now the ruling party of South Sudan.

The FAO said the food shortage has already caused prices to double. It estimates that at least 235,000 people need help.

The agency says the fighting disrupted the region's planting season and also came during the “lean” time of year when household food stocks are at their lowest.

It says the true scale of the problem is not clear because Khartoum has barred aid groups from entering Blue Nile state. A small U.N. team is in Southern Kordofan.