The United Nations Children’s Fund warned Tuesday that some 25,000 children are suffering from severe acute malnutrition in North Korea and require immediate treatment. Unicef is calling for $18 million in donations for its work in North Korea as part of a $2.8 billion appeal to reach 43 million children in humanitarian emergencies around the world.

In North Korea, children are struggling to recover from severe drought that hit four agricultural provinces during 2015 and led to a 20 percent drop in crop production compared with the previous year. The impact will continue into 2016, Unicef said.

“Cereal rations were reduced, impacting the nutritional and health status of women and children,” it said in a statement Tuesday. “In drought-affected provinces, there has been a 72 percent increase in diarrhea among children under 5 years, a leading cause of malnutrition and death.”

Unicef is asking for $8.5 million for nutrition, $5 million for water and sanitation, and $4.5 million for healthcare to meet the needs of the North Korean children. This includes money for lifesaving medication, immunization, prevention and treatment of diarrhea and pneumonia, therapeutic food and access to safe drinking water.

Humanitarian aid for North Korea often lacks sufficient funding because of Pyongyang’s restrictions on humanitarian workers and international concerns over its nuclear ambitions. International aid to North Korea shrinks whenever the capital conducts weapons trials, such as the test of a  miniaturized hydrogen bomb this month, as foreign governments try to pressure its leader, Kim Jong Un, according to the Guardian.

Funding for U.N. agencies in North Korea plummeted from $300 million in 2004 to less than $50 million in 2014. About 70 percent of North Koreans lack secure access to food, and nearly one-third of children under 5 have stunted growth.

“[North] Korea is both a silent and underfunded humanitarian situation,” Ghulam Isaczai, the U.N.'s resident coordinator for North Korea, said in a statement last year, according to Reuters. “Protracted and serious needs for millions of people are persistent and require sustained funding.”