Russia's Defence Ministry said on Wednesday the Russian warship Ivan Hurs had been attacked unsuccessfully in the early morning by three Ukrainian uncrewed speedboats in the Black Sea, on the approaches to the Bosphorus strait.
In a statement posted on Telegram, the ministry said the warship had been protecting the TurkStream and Blue Stream gas pipelines - which carry gas from Russia to Turkey, partly across the Black Sea - and "continues to fulfil its tasks".
The statement appeared likely to raise tensions in the Black Sea, where Russia only agreed last week, one day before a self-imposed deadline, to extend a deal allowing Ukraine to export grain safely from its seaports.
No comment was immediately available from Kyiv.
The ministry cited the attack as a justification for Russia expanding measures to defend its pipelines, though no mention was made of any implications for the safety of grain ships.
Unexplained explosions last September ruptured the Nord Stream 1 and 2 pipelines bringing gas from Russia under the Baltic Sea to Germany.
Despite allowing the Grain Initiative to continue for another two months, Russia continues to complain that the West is not fulfilling its side of the bargain by removing obstacles to the export of Russian grain and fertilisers.
Ukraine accused Russia on Tuesday of effectively cutting the Ukrainian port of Pivdennyi, known as Yuzhny in Russian, out of the deal as Russia complained that it had been unable to export ammonia via a pipeline to Pivdennyi.
Turkey is one of the sponsors of the Black Sea grain deal, and has declined to follow the West in imposing economic sanctions on Russia.
After losing the use of its Baltic Sea pipelines, Russia is keen that Turkey should become even more of a hub for Russian energy exports.
TurkStream carries gas westward from Russia's Taman peninsula across the width of the Black Sea to a point west of the Bosphorus on the coast of European Turkey.
Blue Stream, however, crosses the eastern Black Sea from north to south, making landfall in the Turkish port of Samsun, around 700 km east of the Bosphorus by sea.
The Ivan Hurs is a medium reconnaissance ship launched in 2013. The Defence Ministry said all the naval drones "were destroyed by fire from the standard armament of a Russian ship 140 km northeast of the Bosphorus".
(Reporting by Reuters; Writing by Kevin Liffey; Editing by Conor Humphries and Ed Osmond)
