Kyiv's maritime grain exports were halted after Russia pulled out of a landmark agreement that allowed the vital shipments.

The July deal to unlock grain exports signed between Russia and Ukraine and brokered by Turkey and the United Nations, is critical to easing the global food crisis caused by the conflict.

"(A) bulk carrier loaded with 40 tons of grain was supposed to leave the Ukraine port today," Infrastructure Minister Oleksandr Kubrakov tweeted.

"These foodstuffs were intended for Ethiopians, that are on the verge of famine. But due to the blockage of the 'grain corridor' by Russia the export is impossible," the Ukrainian minister said.

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.

Russia's defence ministry alleged Sunday the attack drones had "Canadian-made navigation modules", saying it had recovered debris from some of the weapons in the sea.

Specialists had "conducted an examination of Canadian-made navigation modules installed on the marine unmanned vehicles", the ministry said.

On Saturday Russia announced its suspension after accusing Kyiv of a "massive" drone attack on the 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".

UN Secretary-General Antonio Guterres on Sunday expressed "deep concern" about the situation, his spokesman said, and delayed his departure for an Arab League Summit in Algiers by a day "to focus on the issue".

The EU on Sunday urged Russia to "revert its decision".

- Enough grain to 'feed millions' -

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 10 vessels both outbound and inbound waiting to enter the corridor."

Turkey's defence ministry later Sunday said ships would not leave Ukraine "during this period" but Turkey would continue checks of ships in Istanbul carrying Ukrainian grain "today and tomorrow".

It also said Russia had formally notified Turkey of its suspension but "Russian personnel remained at the coordination centre" in Istanbul.

Ukraine's foreign minister said on Twitter that Russia was blocking "two million tons of grain on 176 vessels already at sea" that he said was "enough to feed seven million people."

He accused Moscow of having planned to "resume its hunger games" in advance and said the Black Sea explosions were "220 kilometres away from the grain corridor".

- 'Peddling false claims' -

Kyiv and the UN earlier urged that the agreement remain in force.

Ukrainian President Volodymyr Zelensky called Russia's move "an absolutely transparent intention of Russia to return the threat of large-scale famine to Africa and Asia".

Sevastopol in Moscow-annexed Crimea has been targeted several times in recent months and serves as the Black Sea fleet's headquarters and a logistical hub for operations in Ukraine.

Russia's army claimed to have "destroyed" nine aerial drones and seven maritime ones in an attack on the port early Saturday.

It alleged British "specialists" 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".

Moscow's military said ships targeted at their Crimean base were involved in the grain deal.

- 'Massive' attack -

Russia had recently criticised the deal, saying its own grain exports have suffered due to Western sanctions.

Mikhail Razvozhayev, the Moscow-installed governor of Sevastopol, said Saturday's drone attack was the "most massive" the peninsula had seen.

Attacks on Crimea, annexed by Moscow in 2014, have increased recently as Kyiv presses a counter-offensive in the south to retake territory held by Moscow.

In early October, Moscow's key bridge linking Crimea to the Russian mainland was damaged by a blast that President Vladimir Putin blamed on Ukraine.

Kyiv said Sunday its troops in the south are "holding their positions and hit the enemy in order to create conditions for further offensive actions."

Moscow-installed authorities in Kherson, just north of Crimea, have vowed to turn the city into a fortress, preparing for an inevitable assault.

burs/raz/gw