KYIV (BLOOMBERG) - Ukraine has suffered US$4.3 billion (S$6 billion) in damage to farmland, machinery and livestock as a result of Russia's invasion, according to the Kyiv School of Economics.

About half of the "already immense" destruction from the war comes from pollution caused by mines and unharvested crops, according to a report by authors Roman Neyter, Hryhorii Stolnikovych, and Oleg Nivievskyi.

Almost a quarter of the total - US$926 million - accounts for damage done to farm machinery due to military activity and occupation, they write.

The "Ukrainian economy is projected to contract by 45 per cent and dozens of millions across the world are threatened with hunger because of disrupted exports of grains from Ukraine and continued damage of its agri-food sector", the report said.

Russia's attacks on key agriculture infrastructure hubs have destroyed large quantities of food. Meanwhile, its blockade of Ukraine's ports has strangled the country's exports, cutting off a key source of revenues and worsening a global food crisis that may spur millions of people to migrate.

Moscow denies targeting civilian installations and infrastructure, despite widespread evidence to the contrary.

Global food prices are near record highs, with millions of tons of grain and vegetable oil stuck in Ukraine.

Efforts to reopen the ports are stumbling, with no sign of progress on a deal, while removing sea mines could take months, according to a United Nations agency.

Farmland in frontline and formerly occupied areas has a high risk of pollution caused by mines which "impose a mortal threat to Ukrainian farmers during the field works", the report said, estimating that US$436 million may be needed for demining.

Ukrainian grain shippers have carved out new export routes via the Baltic Sea to send their crops abroad, but sales remain well short of their normal pace, and the country is expected to run out of room to store coming harvests.

The authors calculate that 5.7 million poultry have died due to the war while US$613 million worth of grain has been stolen from occupied regions of Ukraine and sent to Russia.

"Farm animals are dying directly because of the hostilities and because of the farmers' inability to either access the farm or get animal feed and provide animals with needed veterinary support and care," the report said.