The Black Sea deal brokered by the UN and Turkey expired on Monday, with Moscow unwilling to renew it for another 60 days.
The US led western condemnation of what it called an “act of cruelty”, as Ukraine said it would try to keep the sea corridor open and use alternative routes by land.
UN Secretary General Antonio Guterres said he was “deeply disappointed” by a Russian move that would “strike a blow to people in need everywhere”.
Moscow said the Black Sea was once again a danger zone for shipping as safety guarantees under the deal were withdrawn.
Kremlin spokesman Dmitry Peskov said Russia would return to the pact when its demands on exporting its own produce were met.
“The Black Sea agreements ceased to be valid today,” he said.
“Unfortunately, the part of these Black Sea agreements concerning Russia has not been implemented so far, so its effect is terminated.”
The pact had been credited with easing the global food crisis unleashed by the war between Russia and Ukraine, two of the world's top agricultural producers that produce an estimated 30 per cent of the world's wheat.
About 33 million tonnes of goods were exported under the deal, according to UN figures, including 16.9 million tonnes of corn, 8.9 million tonnes of wheat and large quantities of sunflower oil.
The deal gave safe passage to ships sailing through the Black Sea on condition that Russia and Ukraine could both inspect their cargo.
European Commission President Ursula von der Leyen condemned what she called a “cynical move” by Russia, which said it had notified the UN, Turkey and Ukraine that it would not support a renewal.
Turkish President Recep Tayyip Erdogan said he would speak to his Russian counterpart Vladimir Putin, while Germany appealed to Moscow to make an extension possible. The UK accused the Kremlin of using food as a weapon.
US ambassador to the UN Linda Thomas-Greenfield told reporters in New York: “While Russia plays political games, real people will suffer.”
Sarah Champion, the chairwoman of the UK Parliament's international development committee, told The National the deal should be “urgently reinstated”.
“Over half of the grain exported under the scheme is currently going to lower income countries,” she said.
“Any disruption to exports from Russia’s withdrawal from the deal is likely to hit the poorest people in some of the poorest countries the most, and could disrupt humanitarian operations sending Ukrainian grain to countries in crisis like Afghanistan, Ethiopia and Yemen.”
The charity Save the Children said Lebanon faced food insecurity while Tunisia faces an “increase in poverty and hunger”.
“The grain deal was a lifeline to millions of boys and girls facing devastating hunger. Not renewing this initiative will prove catastrophic for children around the world and cost thousands of lives,” said charity representative Nana Ndeda.
Germany's Foreign Minister Annalena Baerbock told reporters in New York that Mr Putin was using “hunger as a weapon against the entire world in his brutal war of aggression”.
“The fact that the Russian President has announced that he is once again interrupting the Black Sea Initiative, which brings grain from Ukraine to the entire world, makes it clear that he has no regard for the globe’s weakest.”
UK Foreign Secretary James Cleverly condemned the Russian leader’s actions, pointing to UN estimates that it could condemn millions more people to hunger.
“Putin is using food as a weapon,” he said. “The UK strongly condemns Russia’s withdrawal from the Black Sea Grain Initiative.
“This decision hurts the world’s poorest.
“The UN estimates that without the grain provided by the BSGI, the number of undernourished people worldwide could increase by millions.
“The best way for Russia to address concerns around global food security would be for it to withdraw its forces from Ukraine and end the war.”
Opening seaports such as Odesa allowed Ukraine to export a greater volume of grain than on complicated road and rail routes. Railway wagons have to change wheels at the Polish border because of different track gauges.
Dmytro Senik, Ukraine’s ambassador to the UAE, said the government was looking to increase the capacity of inland waterways.
“The challenges will be there as these three ports on the Danube river are already at full capacity. But we have already started work building new terminals,” he said.
President Volodymyr Zelenskyy said Ukraine would “do everything” to keep the Black Sea lanes open.
“We are not afraid,” said Mr Zelenskyy, who added some ship owners had indicated they were willing to keep sailing in the Black Sea.
Russia says assurances by the UN that it would be able to sell its own goods have not been fulfilled. It blames sanctions that western governments maintain do not apply to food.
Mr Guterres had lobbied for the deal's renewal but Mr Putin spurned his proposal to ease restrictions on a Russian bank. The UN chief also said he was “deeply” disappointed that his new proposal to extend the deal which he sent to Russian President Putin went “unheeded”.
He said the UN will not stop its efforts to enable “unimpeded access” to global markets for food products and fertilisers from both Ukraine and the Russian Federation.
Washington’s ambassador to the UN Linda Thomas-Greenfield meanwhile called Russia’s actions “another act of cruelty” and said Moscow is “playing games” and holding “humanity hostage”.
She called on the international community to urge Russia to reverse its “decision, resume negotiations extend, expand and fully implement” the initiative.
Another Russian grievance was that some of the grain went to rich countries, although the UN says developing nations have received more than half the produce.
Ms von der Leyen said the EU would keep using land routes to bring Ukrainian products to market.
Ukrainian wheat has been delivered to countries such as Afghanistan, Sudan, Djibouti, Ethiopia, Kenya, Somalia and Yemen to fight hunger. The World Food Programme had described the deal as a lifeline that had helped food prices drop by 23 per cent from their peak in the war's early stages.
Mr Putin's mind was made up before an overnight attack on a Crimean bridge and there was no link to the grain deal decision, Mr Peskov said.