A Russian warplane destroyed a Ukrainian reconnaissance vessel in an area in the Black Sea where Russian gas extraction facilities are located, the Russian Defense Ministry said early on Tuesday.
The ministry said in a short statement that the Ukrainian vessel had been destroyed by an SU-30 aircraft from Russia's Black Sea Fleet.
There was no immediate comment from Ukraine, which rarely comments publicly on its operations inside Russia or on Russian-controlled territory but which Moscow has accused of stepping up attacks on Russian interests using uncrewed naval drones.
Russian-backed officials in Crimea, which Russia seized and annexed from Ukraine in 2014, said in June last year that Ukrainian forces had attacked drilling platforms in the Black Sea owned by Chernomorneftegaz, an oil and gas company.
At least three people were wounded in one incident and work on three drilling platforms was suspended, they said at the time.
Russia seized Chernomorneftegaz from Ukraine's national gas operator Naftogaz as part of Moscow's 2014 annexation. The company is under US and European Union sanctions.
The rigs are located off Ukraine's southern Black Sea coast, 71 km (44 miles) from the port of Odesa, which remains under the control of Ukrainian forces.