KYIV, UKRAINE (AFP) - It would take Ukraine a decade to build infrastructure to replace its Black Sea ports, whose blockade by Russia is preventing grain exports around the world, Ukraine's deputy agriculture minister said Friday (June 24).

Millions of tonnes of wheat and other grain have been stuck in Ukrainian ports since Russia invaded in February, sparking global concern about hunger and food prices.

"For alternative routes, it would take 10 years of investment to try to build the necessary infrastructure to replace this Black Sea port infrastructure, which we spent about 20 years building, starting in 2000," Taras Vysotskiy said in an interview with AFP.

"These alternative routes are important" but can only carry around a third of Ukraine's exports, he said.

Ukraine's Western allies are looking for ways to unblock the ports, particularly Odesa, the main point of departure for the country's agricultural produce.

"Without very concrete guarantees allowing ships to enter and leave safely, we cannot allow such actions," Vysotskiy said, adding that Russia was not ready to provide these assurances.

Meanwhile, about 20 million tonnes of grain from last year's harvest are still stuck in Ukraine, he said.

But he said the grain could be "stored very efficiently for up to two years" under the right conditions.

Referring to a recent Russian strike on one of Ukraine's largest grain terminals in the southern city of Mykolaiv, he estimated "10 to 15 per cent of the port infrastructure was destroyed by rockets from Russia".

Repeating accusations already made by Ukrainian President Volodymyr Zelensky, he said Kyiv had "evidence that about half a million tonnes were stolen from the regions partially occupied" by Russia, specifically the regions of Kherson, Zaporizhzhia and Luhansk.

"We have received evidence from satellite images showing grain has been transported to Syria," Vysotskiy added.

He said Ukraine has informed countries of the risk of transporting stolen grain, adding that ships had carried it from Crimea, which was annexed by Russia in 2014.

The deputy minister said Ukraine had no contact with Syria but added that other countries had been offered grain from Russia suspected of being stolen from Ukraine.

"We have been informed that Egypt was offered grain (from Ukraine) but turned it down," Vysotskiy said.