North Korea's staple food output has improved but the poverty-stricken country is still struggling to eradicate malnutrition and provide its people with vital protein, UN agencies said Tuesday.

Overall production for the main 2012 harvest and 2013 early season crops is expected to be 5.8 million metric tonnes, up 10 percent on 2011-2012, according to the Food and Agriculture Organization (FAO) and World Food Programme (WFP).

But their report said the figures "should not mask an ongoing struggle with undernutrition and a lack of vital protein and fat in the diet, especially for an estimated 2.8 million vulnerable people".

North Korea has suffered regular chronic food shortages under the Kim dynasty, with the situation exacerbated by floods, droughts and mismanagement. During a famine in the mid to late-1990s, hundreds of thousands died.

A joint assessment mission from the FAO and WFP visited all the North's agricultural provinces between late September and early October -- around the time of the main annual cereal harvest.

It estimated the country would need to import 507,000 metric tonnes of cereals to meet its basic food needs, but the government's import target was 300,000 metric tonnes, leaving a deficit of 207,000 metric tonnes if it was met.

The figure was the lowest in many years but the mission voiced concern over a 30 percent decrease in soybean production and limited quantities of vegetables, perpetuating a "chronic lack" of key proteins, oils, fats and vitamins.

Soybean production was hit by a prolonged dry spell in the first half of 2012 but the impact on maize was largely mitigated by irrigation as people were mobilised on a huge scale to water crops by hand.

"The new harvest figures are good news, but the lack of proteins and fats in the diet is alarming", the WFP's North Korea country director Claudia von Roehl said.

"We must double our efforts to reach two million children with a steady stream of nutritious foods and so provide a more balanced, healthy diet," she added.

Kisan Gunjal, FAO economist and co-leader of the mission, said: "The country needs to produce more protein-rich foods like soybean and fish and to put more effort into growing two crops a year so a more varied diet is available for everyone."

UN agencies said in June that about one in three children aged under five in North Korea are stunted because of malnutrition.