As countries shut down borders and restrict trade, risks are growing in the world's complex food supply networks.

Qu Dongyu, director-general of the UN Food and Agriculture Organization (FAO) made an appeal on Tuesday, urging international efforts to minimize the pandemic's impact on food supply chains, and to prevent a food crisis.

He said as countries move to enact measures aiming to halt the spreading COVID-19 pandemic, efforts should be made to minimize potential impacts on food supply or unintended consequences on global trade and food security.

There are also moves by some countries that are affecting supply.

Kazakhstan has banned exports of wheat flour, buckwheat, sugar, and some vegetables. Russia has suspended processed grain exports. Vietnam, the world's third largest rice exporter, is stockpiling rice and has suspended new exports contracts.

Labor is another concern as farmers have to live by the rules of nature. In some parts of the world, spring is critical for planting and harvests, but travel restrictions are not helping. Julia Kloeckner, the German agriculture minister, said, "Farms and food producers are severely affected by the entry ban on seasonal hands which the German government has imposed. Normally, there are some 30,000 farm hands needed in March, not only in the asparagus harvest, but also in seeding and planting. And in May some 80,000 are needed."

The picture is not all gloomy: countries are working to make sure prices remain stable. China has stepped up efforts to boost pork supplies and to curb rising prices, including releasing more frozen meat from reserves, boosting production and raising meat imports.

The director-general said a globally coordinated response is needed, warning that the pandemic should not become a hunger game.