Russia has suspended participation in a U.N.-brokered deal to export agricultural produce from Ukrainian ports following attacks on ships in Crimea, TASS quoted the defense ministry as saying on Saturday.

Russia said that Ukrainian forces, with the help of drones, attacked ships from the Black Sea Fleet in Sevastopol, the biggest city in Russian-annexed Crimea, in the early hours of Saturday.

"Taking into account... the terrorist act by the Kyiv regime with the participation of British experts against the ships of the Black Sea Fleet and civilian vessels involved in ensuring the security of the "grain corridor," the Russian side suspends participation in the implementation of agreements on the export of agricultural products from Ukrainian ports," the ministry said in a statement.

The ministry said earlier that the drone attacks on Saturday were largely repelled, with minor damage to a Russian minesweeper.

United Nations aid chief Martin Griffiths had said only on Wednesday that he was "relatively optimistic" that the deal that allowed a resumption of Ukraine Black Sea grain exports would be extended beyond mid-November.

Under the July 22 agreement, Ukraine was able to restart its Black Sea grain and fertilizer exports, which had stalled when Russia invaded its neighbor on Feb. 24. The Ukraine export deal was initially agreed for 120 days.