Mark Lowcock, the U.N. aid chief, returned to Beijing from Pyongyang on Thursday, after looking into what is believed to be a precarious food situation in North Korea due in part to natural disasters.

During his four-day visit from Monday, the U.N. undersecretary general of humanitarian affairs and emergency relief coordinator met with North Korea's ceremonial head of state Kim Yong Nam and public health minister Jang Jun Sang.

(Lowcock, right, shakes hands with a North Korean official at Pyongyang airport)

His arrival at Beijing International Airport was confirmed by Kyodo News.

It marked the first time since 2011 that an U.N. aid chief has visited North Korea.

Lowcock said in Pyongyang that a large number of people still need assistance in North Korea, while around 20 percent of children have stunted growth because of malnutrition.

"That figure in 2011 was about 28 percent, so that's an improvement. From 28 percent to 20 percent is an improvement, but 20 percent is still a high number," Lowcock said at a press conference in the capital on Wednesday, according to the United Nations.

"There are still significant humanitarian challenges here," he said, adding that the United Nations is trying to provide $111 million in aid to North Korea to improve areas such as health, water and sanitation, and food security for about six million people.

North Korea has faced food shortages against a backdrop of natural disasters including floods and a failing food distribution policy in the past.

(Shoppers at a Pyongyang supermarket in December 2017)