A British frigate was dispatched to track a mysterious battleship that covertly sneaked in close to Denmark’s coast. The ship turned out to be Russian stealth corvette conducting a complex checkout of battle systems, according to British media.

Russian naval drills in the Baltic Sea drew some heat after British HMS Montrose (a type 23 frigate) had to establish line-of-sight range with an unidentified warship cruising off the territorial waters of NATO-member Denmark on June 19.

In harsh conditions of 30 knot winds, British sailors identified the warship as Russia’s 104-metre-long RFS Soobrazitelny (Project 20381), Steregushy-class stealth corvette, armed with a vast arsenal of anti-ship and air-defense missiles, and anti-submarine torpedoes.

“We picked up a vessel on our radar that was not showing any of the normal behavior expected of merchant vessels or allied warships,” said Lieutenant Chloe Lea, HMS Montrose’s watch officer, as quoted by the Daily Mail.

"We have seen the Russians operate a lot in this area, but this is the closest we have seen them,” she said.

The Royal Navy’s HMS Montrose, based in Plymouth, has a crew of 205 and is armed with Sea Wolf missiles, Harpoon missiles, and Sting Ray torpedoes.

The RFS Soobrazitelny’s basic weapon is an X-35 (NATO code SS-N-25 Switchblade) Uran anti-ship missile complex, Redut anti-air missiles and Paket–NK torpedoes.

Both Russian warships and aircraft were conducting routine maneuvers in international waters, so the British ship left the area.

While HMS Montrose was tracking Soobrazitelny, a Russian Ilyushin IL-20 “Coot” maritime patrol aircraft was circling the British ship, analyzing the radar target signature of the Royal Navy destroyer.

“Both the Russian vessel and aircraft appeared to be carrying out their normal business,” the British Ministry of Defense acknowledged in a statement.

HMS Montrose was taking part in the BALTOPS multinational reinforced exercise that included 14 countries, the biggest NATO military drills in Eastern Europe since the Ukraine political crisis entered its critical phase.

“All our interaction so far has been professional and effective, and we have gained huge benefit from working so closely with our allies in such a busy and challenging environment,” said Commander James Parkin, commanding officer of HMS Montrose.

Three warships of the Steregushy-class stealth corvette series, the prototype Stereguschy, accompanied by Soobrazitelny and Boiky production line ships, have taken part in the latest naval drills, conducting missile firing tests and practicing landings of on-board helicopters in various conditions, including at night time and in motion.

Two days prior to the latest naval encounter, three RAF Typhoon fighter jets were scrambled to head off four separate groups of Russian aircraft taking part in drills in the Baltic.