A World Food Programme (WFP) official said food supply chains in Ukraine are collapsing, with a portion of infrastructure destroyed and many grocery stores and warehouses empty.

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"The country's food supply chain is falling apart. Movements of goods have slowed down due to insecurity and the reluctance of drivers," Jakob Kern, WFP Emergency Coordinator for the Ukraine crisis, told a Geneva press briefing by videolink from Poland.

He also expressed concern about the situation in "encircled cities" such as Mariupol, saying that food and water supplies were running out and that its convoys had been unable to enter the city.

WFP buys nearly half of its wheat supplies from Ukraine and Mr Kern said that the crisis there since the Russian invasion had pushed up food prices sharply.

"With global food prices at an all-time high, WFP is also concerned about the impact of the Ukraine crisis on food security globally, especially hunger hot spots," he said, warning of "collateral hunger" in other places.