The world is facing an "impending global food emergency" that could impact hundreds of millions of people as the coronavirus pandemic threatens already strained supply chains, UN Secretary-General Antonio Guterres warned Tuesday.

"Our food systems are failing, and the Covid-19 pandemic is making things worse," the UN chief said in a statement accompanying a report by the world body.

"More than 820 million people are hungry," he said. "Some 144 million children under the age of five are stunted –- more than one in five children worldwide."

He warned that "this year, some 49 million extra people may fall into extreme poverty due to the COVID-19 crisis.

"The number of people who are acutely food or nutrition insecure will rapidly expand," he said.

"Unless immediate action is taken, it is increasingly clear that there is an impending global food emergency that could have long term impacts on hundreds of millions of children and adults."

Guterres called for better protection for workers in the food sector, for humanitarian aid deliveries to be safeguarded and for support for food producers and distributors to avoid interruptions to the supply chain.

He also wanted more emphasis placed on nutritional programs, including aid to children who lack access to school meals.

The UN chief said it was possible to develop healthy and nutritional food to help eradicate world hunger.

In April, the UN raised the alarm about a potential explosion in the number of people at severe risk of hunger because of the coronavirus pandemic.