Dutch frigate/Russian patrol
© (L) Boudewijn Boots/Twitter; (R) VitalyTimkiv/Sputnik
Dutch frigate HNLMS Evertsen • Russian patrol ship Vasily Bykov
Russian ships are keeping a close eye on NATO, whose three frigates recently crossed into the Black Sea, preparing to sail near Crimea and conduct a joint naval drill with Ukraine and Georgia.

The large patrol ship Vasily Bykov, along with surveillance ship Ivan Khurs, both of Russia's Black Sea Fleet, are closely tracking the movement of NATO vessels in the area, the Defense Ministry said.

The photos and videos from Turkey had earlier showed three NATO frigates passing through the Bosporus Strait and entering the Black Sea on Thursday. The ships - Canadian HMCS Toronto, Spain's Santa Maria, and Dutch HNLMS Evertsen - are set to visit the Ukrainian port of Odessa, near Russia's Crimea. They are later scheduled to participate in the Sea Shield 19 naval drill, together with ships from Ukraine and Georgia.

NATO has stepped up its posturing in the Black Sea in recent years. In January, Washington dispatched destroyer USS Donald Cook to spend more than a week in the region, training with the Georgian Navy. A month later, the ship paid a visit to Ukraine, docking in Odessa.