SIMFEROPOL, December 16 /TASS/. The Russian Federal Security Service border department for Crimea has sent the Ametist escort ship to protect Chernomorneftegaz’s boring rigs from Ukrainian warships, a FSB source told TASS.

According to the border department, a ship belonging to Ukraine’s State Border Service approached a Tavrida boring rig, which belongs to Russia’s Chernomorneftegaz company, and asked its captain questions about the crew and the purpose of the Russian drilling rig’s presence in that area. The rig’s captain provided no such information to the Ukrainian side.

After that, the Ukrainian warship sailed further to take photos of the Golitsinsky gas condensate deposit.

For the safety of Tavrida crew and for the purpose of protecting Russia’s economic interests, the Ametist escort ship has been sent to that area. Having arrived at the Odessa and Golitsynsky fields, the Ametist discovered two Ukrainian naval ships nearby, the Crimean border department said.

The Ametist is still patrolling the Black Sea area where Chernomorneftegaz is operating to protect Russia’s economic and other lawful interests.

The deposits on the Black Sea shelf became Russian after Crimea had reunited with Russia after the March 2014 referendum. But Ukraine is claiming them back. Ukrainian President Pyotr Poroshenko said Kiev would seek the return of the Odessa and Golitsynsky deposits in court.

Chernomorneftegaz created in 1979 is the only oil and gas producing company in Crimea. It develops oil and gas fields in the Black and Azov Seas.