A severe drought is expected to worsen serious food shortages in North Korea, a South Korean expert said Wednesday, as the UN food agency reported that three million people urgently need food aid.

A long dry spell has persisted throughout the North since late April, with some western coastal areas receiving just one tenth of the usual rainfall during the period, according to Pyongyang's state media.

Forecasters say the dry spell is likely to last at least another week.

"Drought has already considerably affected early-season crops such as wheat, barley and potatoes," Kwon Tae-Jin, a senior researcher at the South's state-run Korea Rural Economic Institute, said in a report.

The drought is likely to deprive the North of 86,000 tonnes of food, some 17 percent of early-season crops, Kwon said.

"If the dry spell continues until the end of June, it will have a very serious impact on the main-season crop of maize," Kwon told AFP.

North Korea harvests some 1.8 million tonnes of maize every year, about the same amount as the rice harvest. Maize and rice are the two staples of the impoverished state, he said.

The drought has hit 196,882 hectares (486,298 acres) or 17 percent of North Korea's total farmland, the UN's Food and Agriculture Organisation (FAO) said in a report posted on its website Monday.

Any drop in production was likely to add to the food shortfall and worsen food insecurity in the country, it said.

"Three million vulnerable people, mainly living in the five most food-insecure provinces of Yanggang, Jagang, North Hamkyong, South Hamkyong and Kangwon, are in urgent need of international food assistance," it said.

The assessments are at odds with that of the conservative South Korean government.

The North's food situation "is not so serious as to fall into a level of crisis", foreign ministry spokesman Cho Byung-jae said Tuesday, adding the South has no plans to resume government food aid at present.

The current Seoul government stopped annual major food and fertiliser shipments in 2008. It has permitted humanitarian aid by civic groups, mostly modest in scale.