North Korea needs immediate food assistance after heavy rains killed scores of people and submerged vast swaths of farmland, according to UN office statement.
Thursday's UN report said torrential rains caused severe damage to homes, public buildings, infrastructure and farms, affecting maize, soybean and rice fields.
The worst-hit areas are Anju city and Songchon County in South Phyongan Province, as well as Chonnae County in Kangwon Province, where residents are in dire need of emergency food aid, it said.
Some 36,000 families in Anju do not have access to clean water; wells are contaminated due to overflow of pit latrines and open drainage, raising the risk of a diarrhea outbreak, the report said.
A city official told The Associated Press earlier this week that it was the worst disaster in Anju's history.
The assessment was released by the UN resident coordinator's office in Pyongyang following visits to flood-stricken areas in North Korea earlier this week.
Floods caused by two storm systems last month killed at least 119 people and left tens of thousands homeless, according to the North's state media.
The flooding, which occurred on the heels of a severe drought, renewed concerns about North Korea's ability to feed its people.
Chronic food shortage
In June, the UN said two-thirds of the country's 24 million people are coping with chronic food shortages.
North Korean officials have asked the UN to prioritise the release of emergency supplies, including food and fuel, Martin Nesirky, spokesman for UN Secretary-General Ban Ki-moon, told reporters in New York on Thursday.
Aid groups have donated emergency supplies, including the British-based charity ShelterBox, which dispatched 270 tents to North Korea, according to Howard Chang, a spokesman for Rotary International, who provides funding to ShelterBox.
The US government gave $900,000 in relief supplies for North Korea after deadly floods last year.
A subsequent plan this year to send 240,000 tons in food aid in return for nuclear concessions was scuppered when North Korea tested a long-range rocket in April.
Washington said that step undermined confidence that North Korea would stick to its agreement to allow proper monitoring of food distributions.