It remains unclear if the commitments to stop attacks and ensure safe shipping in the Black Sea, which came with many caveats, could come into effect soon.

Britain urged Russia on Tuesday to agree to the "full, immediate and unconditional ceasefire" proposed by Ukraine after both countries reached a truce covering the Black Sea and energy strikes. Britain's foreign office said in a statement it was in close contact with the United States and Ukraine following the conclusion of talks in Riyadh.

But Russia said the naval ceasefire would only come into force after a number of sanctions against its food and fertiliser trade were lifted. US officials have been separately meeting negotiators from Moscow and Kyiv in Riyadh with the aim of brokering a truce between the two sides.