United Nations teams were heading for flood-hit areas of North Korea to assess possible aid, a UN official said Tuesday, after Pyongyang reported scores dead and tens of thousands homeless.

The country's official news agency published photographs which appeared to show large swathes of submerged land and people wading through thigh-high water or taking refuge on rooftops.

UN officials already based in the North will visit the two worst-affected counties "to see what help if any the UN country team can provide", said UNICEF's Bangkok-based regional spokesman Christopher de Bono by email.

The teams have left Pyongyang, one heading for South Pyongan province in the west of the country and another for Kangwon province in the east, he said.

The flooding represents a challenge for Kim Jong-Un, new leader of a country which has grappled with severe food shortages since a famine in the 1990s killed hundreds of thousands.

Following an inspection visit last autumn, UN agencies estimated that three million people would need food aid this year even before the deluge.

Widespread deforestation, to collect firewood or clear land for crops, has made the impoverished nation increasingly prone to serious flooding which disrupts agriculture.

On Saturday the official news agency said a week-long flood earlier in July had left 88 dead, injured 134, and made almost 63,000 people homeless.

More than 30,000 hectares (74,000 acres) of crops were washed away or submerged, with roads and factories destroyed, it said.

On Sunday state media reported strong winds and heavy rain were battering parts of the country, including the capital Pyongyang. The official news agency predicted that "most regions will face huge damage".

Prime Minister Choe Yong-Rim visited Songchon county, one of the worst-hit areas in South Pyongan province, to assess damage and console residents, the news agency said Tuesday.

Choe and other officials discussed emergency transport of relief materials "while paying primary attention to stabilising the people's living" in flood-hit areas, it said.

He also inspected damage in Sinyang County in the same province and stressed the need for substantial afforestation.

The United States reached a deal in February to offer the North 240,000 tonnes of food in return for a freeze on nuclear and missile tests.

But the plan was scrapped after Pyongyang's failed rocket launch in April, seen by the US and its allies as an attempted ballistic missile test.