The United Nations refugee agency says food insecurity is forcing a growing number of South Sudanese to seek refuge in Sudan.

UNHCR said Tuesday that heightened food insecurity and unrest in parts of South Sudan, especially in two northwestern states, has led to the flight of some 38,000 people into East and South Darfur since the end of January.

The agency said there is concern the situation could quickly worsen.

It said many of the new refugees are in need of humanitarian assistance, with many children separated from their families.

The U.N. says 2.3 million people have fled their homes since South Sudan erupted into violence in December 2013.