An agreement was reached today to allow the transportation of wheat from Ukrainian ports, the agreement was mediated by Turkey and the UN.

A blockade imposed by Russia has sent food prices soaring and left millions at risk of starvation.

How much is the blocked amount of wheat in Ukraine?

About 20 million tons of grains intended for export are blocked in the country.

Ukrainian President Volodymyr Zelensky has said that this could rise to 75 million tonnes after this year's harvest.

The war also means that this year's harvest will be smaller.

Up to 30 percent of the 86 million tons of grain that Ukraine normally produces will not be harvested, says Laura Wellesley, a food security specialist at the Chatham House Institute.

How has the lack of wheat affected other countries?

Ukraine is usually the world's fourth largest exporter of cereals.

It typically produces 42 percent of the world's sunflower oil, 16 percent of corn, and 9 percent of wheat.

In addition, wheat exports from Russia – the world's largest exporter – are declining.

Western sanctions do not target Russian agriculture, but the Kremlin argues they have hampered exports by raising insurance rates and affecting payments.

Russian ships carrying agricultural products are not banned from EU ports.

Ukraine and Russia typically supply over 40 percent of Africa's wheat, the African Development Bank says.

But the war has led to a shortage of 30 million tons of food in Africa, the bank says.

This has contributed to a 40 percent increase in food prices across the continent.

Similarly, Yemen normally imports more than one million tons of wheat annually from Ukraine.

The drop in supplies between January and May caused the price of flour to rise by 42 percent and bread by 25 percent in Yemen, the UN says.

In Syria, another major importer of Ukrainian wheat, the price of bread has doubled.

International wheat prices have fallen following news of the deal.

However, Laura Wellesley says that unless the massive distribution of wheat from Ukraine begins, many countries in the Middle East and Africa will lose out.

"This would further increase the price of bread within those countries, which would cause a great social upheaval," she says.