Pedestrians walk on a square in front of a Stalin-era skyscraper under a cloudy day in Moscow on Saturday. AFP

Russia on Saturday suspended its participation in a landmark agreement that allowed vital grain exports from Ukraine, blaming alleged drone attacks on Russian ships in Crimea.

However, Turkey has not been "officially notified" by Russia of the withdrawal from the Ukraine grain deal, of which Ankara and the United Nations are guarantors, a Turkish security source told AFP on Saturday.

Russia made the announcement after its army accused Kyiv earlier on Saturday of a "massive" drone attack on its Black Sea fleet, while Britain bluntly rejected Moscow's claims its specialists were involved.

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

The agreement already allowed more than nine million tonnes of Ukrainian grain to be exported and was due to be renewed on Nov.19.

"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.

Sevastopol in Moscow-annexed Crimea, which has been targeted several times in recent months, serves as the headquarters for the 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 in the port early on Saturday.

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 on Saturday that Moscow would raise the blasts and the alleged drone attack at the UN Security Council.

The British defence ministry said this "invented story says more about arguments going on inside the Russian Government than it does about the West."

Agence France-Presse