Moscow has suspended its participation in a UN-backed deal with Kyiv that unblocked the movement of Ukrainian grain out of its southern ports, threatening to deepen the global food crisis.

Russia linked its decision to pull out of the deal to an attack on Saturday on ships in the port of Sevastopol in the Crimean peninsula, which Russia annexed from Ukraine in 2014.

It blamed the attack on Ukrainian armed forces, claiming air defences shot down Ukrainian drones but autonomous explosive boats had caused damage to navy vessels and energy facilities.

“In connection with the actions of the Ukrainian armed forces . . . the Russian side cannot guarantee the safety of civilian dry cargo ships participating in the Black Sea Initiative, and suspends its implementation from today for an indefinite period,” the foreign ministry said.

It also claimed without evidence that British specialists were involved in the attack and said it had instructed its representatives at the Joint Coordination Center in Istanbul, which manages the deal, to suspend activities.

Russia has been hinting at its desire to pull out of the deal for some time. Vladimir Putin has repeatedly expressed dissatisfaction with the deal in recent weeks, claiming it was not sending grain to “the poorest countries”.

UN data shows that rich countries received more than half of the shipment volumes led by Spain. Middle-income countries including Turkey and China accounted for about a quarter of the total, while lower and lower-middle income countries such as Egypt and Ethiopia received just over a fifth. 

The UN has not billed the agreement as intended to send grain directly to poorer countries, saying instead that it was supposed to make grain purchases more accessible for poor countries. The deal was supposed to lower market prices that were sent soaring by Russia’s invasion of Ukraine.

Ukraine said Russia was using a false pretext for pulling out of the deal.

“We have warned of Russia’s plans to ruin the Black Sea Grain Initiative,” Ukraine foreign minister Dmytro Kuleba said on Twitter.

“Now Moscow uses a false pretext to block the grain corridor which ensures food security for millions of people. I call on all states to demand Russia to stop its hunger games and recommit to its obligations.”

In a statement the ministry said that Russia’s actions call into question “the feasibility of [the corridor’s] further functioning”. Saturday’s announcement was “the embodiment of Moscow’s course to destabilise global food security under the pretext of recent events in Sevastopol”, it said.

Kyiv called on the UN and Turkey as guarantors of the grain deal to “send Russia a clear signal about the unacceptable hold [on] hundreds of millions of people around the world, including Africa, Asia and Latin America”.

Mykhailo Podolyak, an adviser to Ukrainian president Volodymyr Zelenskyy, tweeted that Russia was guilty of “nuclear blackmail, energy terror, grain blockade”.

“Putin turned food, cold and prices to weapons against the world. Putin’s Russia is waging a hybrid war against Europe, taking Africa and Middle East hostage,” he said.

Earlier this month the Financial Times reported that the UN-backed deal, which had enabled Ukraine to export millions of tonnes of wheat, was under strain as a surge in the number of cargo ships aiming to cross the Black Sea had caused a backlog.

The UN said it was in touch with Russian authorities on the matter.

“It is vital that all parties refrain from any action that would imperil the Black Sea Grain Initiative which is a critical humanitarian effort that is clearly having a positive impact on access to food for millions of people around the world,” said Stéphane Dujarric, spokesman for the UN secretary-general.

“Russia in entering this agreement recognised its responsibility to ensure that the ongoing conflict does not jeopardise global food security,” said John WH Denton, head of the International Chamber of Commerce, which was involved in the development of the deal.

“There will no doubt be claims and counterclaims about today’s incident in the Black Sea. But both governments must recognise that there is a greater — and global — humanitarian imperative to restore the agricultural shipping corridor without delay,” Denton said.

“Letting this deal fail is not an option for the millions counting on it for their daily existence across the developing world,” he said.