Two Russian military frigates tracked a Canadian warship carrying Stephen Harper in the Baltic Sea for several hours Wednesday – coming within seven nautical miles as part of the cat-and-mouse game being played by Moscow and NATO in the waters off Eastern Europe.

Mr. Harper was spending a day on HMCS Fredericton, a frigate that since late December has been part of the North Atlantic Treaty Organization mission to reassure Eastern Europe members of the military alliance that they will be protected should Russian aggression in Ukraine spread to other countries.

The Russian vessels appeared on the horizon Wednesday about mid-morning local time when the Canadian warship was about a 15 to 18 nautical miles off the northern coast of Poland. Moscow has a naval base in nearby Kaliningrad, a tiny Baltic coast enclave separated from the rest of Russia.

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Mr. Harper's 20-hour stay on the Fredericton was kept under wraps for security reasons at the request of the Canadian military.

Defence Minister Jason Kenney, who accompanied Mr. Harper on the sailing in the Baltic Sea, said he believed the Russian frigates' movements were deliberate.

"Starting three hours ago, they changed course due west and headed in the trajectory of Fredericton," he told reporters as the Russian ships closed in on HMCS Fredericton before breaking off again.

Asked for his assessment of what was happening, Mr. Kenney shrugged. "It is what it is."

The ship's crest of HMCS Fredericton is a Bengal tiger and its motto is "Stalker of the seas" – and this year, thanks to Russian President Vladimir Putin, the Canadian's vessel's mission is more than just training exercises.

It has visited 17 European ports and one African port over the last six months, conducting military exercises in the Black Sea, Mediterranean and the Baltic as part of a show of force.

In 2014 Russia's relationship with the West has undergone a dramatic shift after Moscow seized and annexed Crimea.

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It's transformed from a potential partner back to a rival like the days of the Soviet Union, a change that's also breathed new life into NATO.

The crew of the Fredericton say they know this deployment is unlike others.

"The difference in this deployment is there's a purpose to it," Chief Petty Officer 2nd Class Rodney Helpard, 51, said.

It's "to let NATO nations know the alliance is still a strong entity – and we're still able to come together and do what we were originally designed to do."

It feels good, the crewman said.

"It's nice to see NATO with a bit of teeth."

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Air Force Sergeant Michael Muise, 46, who serves as the Fredericton's meteorologist, said the change in the relationship with the Russians is evident.

The Fredericton is taking part in another allied exercise this month and for the second year in a row, Moscow's navy was not invited.

"It almost seems that focus is starting to head back to that Cold War mentality," Sgt. Muise said.

Encounters with the Russians increase the closer NATO vessels come to Moscow's territory.

On Monday, for instance, a Russian helicopter flew within several hundred yards of the Fredericton.

"I assume they were taking a look," Commander Jeff Murray, who captains the Fredericton.

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"I fully expect they were keeping situational awareness as all militaries do," he said of the Russian frigates tracking his warship on Tuesday.

Sgt. Muise said he's not surprised Russians are shadowing Canadian vessels.

"We're in their backyard. It's not a surprise to us that they're coming out and sticking their nose in here.

"Especially with Baltic Ops where it's like they're the kid who didn't get invited to play in the sandbox."

The public relations outreach that HMCS Fredericton conducts at many port of calls throughout Eastern and Central Europe is probably just as important as the naval exercises and show of force.

In a determined show of soft diplomacy, the Fredericton frequently hosts local diplomats, politicians and journalists at the ports they visit. The message when foreign visitors come aboard is to reinforce the NATO reassurance mission. "It's 'We're here, we've got your back'," Sgt. Muise said.

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"We kind of laugh at them and call them dog-and-pony shows or cocktail parties," he said of regular events.

"But if you see the actual results of what they do and how it reassures our NATO partners, it really does demonstrate that we're here and we have a presence here."