Thirty-four countries - nearly 80 per cent of them in Africa - do not have enough food for their people because of conflicts, drought and flooding, a United Nations report has said.

The Food and Agriculture Organisation's Crop Prospects and Food Situation report said conflicts in Iraq, Syria, Yemen, Somalia, and the Central African Republic had taken a heavy toll on agricultural production, worsening the humanitarian crisis in those countries.

The impact of these conflicts extends to neighbouring countries that are hosting refugees, straining food resources, it said.

Congo is not only dealing with nearly 100,000 refugees from Central African Republic but conflict in the east, where an estimated 1.5 million people are displaced, and flooding related to El Nino, which has affected about half a million people, the report said.

The FAO said drought associated with El Nino "sharply reduced" 2016 crop production prospects in southern Africa. It said dry conditions linked to El Nino may also affect the planting of crops for the main growing season in areas of Central America and the Caribbean for the third consecutive year.

Dry conditions have also lowered expectations for harvests this year in Morocco and Algeria, the report said.

The FAO also warned that drought and floods in North Korea in 2015 "sharply decreased" food crop production in the early and main growing seasons.

"With a reduced harvest in 2015, the food security situation is likely to deteriorate compared to the situation of previous years, when most households were already estimated to have borderline or poor food consumption rates," the report said.

The number of countries needing outside food assistance grew from 33 in December, after the addition of Swaziland, where El Nino-associated drought conditions have sharply lowered 2016 cereal crop production prospects.

Other countries on the FAO list facing food shortages are Zimbabwe; Burkina Faso; Chad; Djibouti; Eritrea; Guinea; Liberia; Malawi; Mali; Mauritania; Niger; Sierra Leone; Burundi; Republic of Congo; Ethiopia; Kenya; Lesotho; Madagascar; Mozambique; South Sudan; Sudan; Swaziland; Uganda; Afghanistan; Myanmar (Burma); and Nepal.

Elsewhere, the report said, the outlook for 2016 crops already in the ground, mostly winter grains in the northern hemisphere, is generally favourable and early forecasts indicate large wheat crops in most Asian countries.

The FAO's first forecast for wheat production in 2016 is 723 million tons - 10 million tons below the record output in 2015.