UNITED NATIONS — The U.N. humanitarian chief warned Tuesday that nearly 6 million people are struggling to get food in West Africa’s Sahel region and severe malnutrition is threatening the lives of 1.6 million children.

Mark Lowcock said in a statement that these levels haven’t been seen since a crisis in 2012 “and the most critical months are still ahead.”

He said the rapid deterioration in recent months in Burkina Faso, Chad, Mali, Mauritania, Niger and Senegal “reveals an urgent need for more donor support.” He said U.N. plans to respond to the crisis in the six countries are only 26 percent funded and he urged donors for additional support. “We can still avert the worst,” he said.

Lowcock said the crisis was triggered by scarce and erratic rainfall in 2017, “resulting in water, crop and pasture shortages and livestock losses.”

In early May, three U.N. agencies warned that drought, conflict and high food prices would drive millions of people in the Sahel into malnutrition and further insecurity without immediate aid. The World Food Program, the U.N. children’s agency UNICEF and the Food and Agriculture Organization said this could be one of the worst crop seasons in several years.

Fighters affiliated with the Islamic State extremist group and al-Qaida are active in the Sahel, and the three agencies said insecurity in the region has forced tens of thousands of people to leave their homes, led schools to close and disrupted basic social services.

Lowcock, the undersecretary-general for humanitarian affairs, said food has already run out for millions.

“Families are cutting down on meals, withdrawing children from school and going without essential health treatment to save money for food,” he said.

“Severe acute malnutrition rates in the six countries have increased by 50 percent since last year,” he added. “One child in six under the age of five now needs urgent life-saving treatment to survive.”

Lowcock said he is most concerned about Burkina Faso, Chad, Mali and Mauritania.

In Burkina Faso, the number of people facing “food insecurity” has tripled since last year, he said.