Ukraine's maritime grain exports were halted Sunday after Russia suspended its participation in a landmark agreement that allowed the vital shipments, blaming drone attacks on its ships in Crimea.
The July deal to unlock grain exports signed between Russia and Ukraine and brokered by Turkey and the UN, is critical to easing the global food crisis caused by the conflict.
The agreement had already allowed more than nine million tonnes of Ukrainian grain to be exported and was due to be renewed on November 19.
On Saturday, Russia said it was halting its participation after its army accused Kyiv of a "massive" drone attack on its Black Sea fleet, which Ukraine labelled a "false pretext".
US President Joe Biden called the move "purely outrageous" while Secretary of State Antony Blinken said Moscow was "weaponising food".
The centre coordinating the logistics of the deal said in a statement that no traffic was planned for Sunday.
"A joint agreement has not been reached at the JCC for the movement of inbound and outbound vessels on 30 October," it said. "There are more than ten vessels both outbound and inbound waiting to enter the corridor."
Ukraine and the UN have urged that the agreement remains in force.
"I call on all states to demand that Russia stop its hunger games and recommit to fulfilling its obligations," Ukrainian Foreign Minister Dmytro Kuleba said on Twitter.
Ukrainian President Volodymyr Zelensky called the Russian move "an absolutely transparent intention of Russia to return the threat of large-scale famine to Africa and Asia".
"Just today, more than two million tons of food are in the sea. This means that access to food has actually worsened for more than seven million consumers," he said in his nightly address.
Stephane Dujarric, spokesman for the UN secretary-general, said: "It is vital that all parties refrain from any action that would imperil the Black Sea Grain Initiative which is a critical humanitarian effort".
- 'Peddling false claims' -
Sevastopol in Moscow-annexed Crimea has been targeted several times in recent months and serves as the headquarters for the Black Sea fleet and a logistical hub for operations in Ukraine.
The Russian army claimed to have "destroyed" nine aerial drones and seven maritime ones in an attack on the port early Saturday.
"In light of the terrorist act carried out by the Kyiv regime with the participation of British experts against ships of the Black Sea fleet and civilian vessels involved in the security of grain corridors, Russia suspends its participation in the implementation of the agreement on the export of agricultural products from Ukrainian ports," the Russian defence ministry said on Telegram.
Moscow's forces alleged British "specialists", whom they said were based in the southern Ukrainian city of Ochakiv, had helped prepare and train Kyiv to carry out the strike.
In a further singling out of the UK -- which Moscow sees as one of the most unfriendly Western countries -- Russia said the same British unit was involved in explosions on the Nord Stream gas pipelines last month.
Britain strongly rebutted both claims, saying "the Russian Ministry of Defence is resorting to peddling false claims of an epic scale".
Russia's foreign ministry spokeswoman Maria Zakharova said Saturday Moscow would raise the blasts and the alleged drone attack at the UN Security Council.
Moscow's military said ships targeted at their Crimean base were involved in the grain deal.
The United Nations Coordinator for the Black Sea Grain Initiative, Amir Abdulla, reported that Russia had notified him earlier Saturday of "its concerns about the safety of movements of merchant vessels" under the agreement.
Russia had recently criticised the deal, saying its own grain exports have suffered due to Western sanctions.
- 'Massive' attack -
Mikhail Razvozhayev, the Moscow-installed governor of Sevastopol, said Saturday's drone attack was the "most massive" the peninsula had seen.
City authorities said the harbour was "temporarily" closed to boats and ferries and urged people "not to panic".
Attacks on Crimea, annexed by Moscow in 2014, have increased in recent weeks, as Kyiv presses a counter-offensive in the south to retake territory held by Moscow for months.
Moscow-installed authorities in Kherson, just north of Crimea, have vowed to turn the city into a fortress, preparing for an inevitable assault.
In early October, Moscow's bridge linking Crimea to the Russian mainland -- personally inaugurated by President Vladimir Putin in 2018 -- was damaged by a blast that Putin blamed on Ukraine.
The Russian fleet stationed in the port had also been attacked by a drone in August.
Russia's allegations Saturday came as the Ukrainian army reported fighting in the Lugansk and Donetsk regions in the east, including near Bakhmut -- the only area where Moscow's forces have advanced in recent weeks.
Pro-Russian separatists fighting alongside Moscow also announced a new prisoner exchange with Kyiv, saying 50 will return home from each side.