Eight Russian aircraft flew over the North Sea Wednesday, with six turning back toward Russia and two continuing to the Atlantic Ocean. The Norwegian air force scrambled in response to the aircraft flying in formation, as did aircraft from the United Kingdom that responded to the two bombers that continued on. Other aircraft from the Portuguese air force and NATO forces were involved as well.

Also on Wednesday, four Russian aircraft were detected and intercepted by the Turkish air force in international airspace over the Black Sea, and multiple Russian planes were detected over the Baltic Sea. Portuguese fighters scrambled in response, and the aircraft returned to Russian airspace.

“NATO allies protect their airspace on a 24/7 basis. Allied air defense efforts are focused on stopping unauthorized incursions into NATO airspace and on preventing acts of airborne terrorism,” NATO said following the Russian action.

The bombers and tankers that flew over the North Sea and Atlantic Ocean did not file flight plans or have radio communication with civilian air traffic control officials, posing a risk to civilian flights. Though NATO said the Russian aircraft were continually tracked, Russia already has conducted about three times the number of such flights this year than last, with NATO conducting over 100 intercepts of Russian aircraft so far in 2014. It is standard procedure for the alliance to scramble and intercept similar aircraft it detects over NATO airspace, the alliance said.

Chris Chivvis, a political researcher with the Rand Corp., says Russia’s actions aren’t in line with the recent relative peace seen in its conflict with Ukraine.

“My estimation is right now Russia is not seeking to escalate the situation in Ukraine,” Chivvis says. “It’s possible that this is an effort to demonstrate resolve regarding other parts of Europe, although I’m still not sure what their concern would be or what they would be trying to demonstrate resolve about." 

Russia accepted Ukrainian parliamentary elections held on Sunday as legitimate, although it is supporting separate elections slated to be held in Ukraine's rebel-held eastern provinces this coming Sunday. Russia's actions in Ukraine, including its annexation of Crimea, have continually defied Western calls for respect for the country's sovereignty.

Wednesday's flights weren't the week's first mysterious action by Russian planes. On Tuesday, seven Russian fighter jets were intercepted after flying over the Baltic Sea. Aircraft from Germany, Denmark, Finland and Sweden all responded, even though Finland and Sweden are not NATO members. These Russian aircraft had filed a flight plan but did not maintain communication with civilian air traffic control.

In a speech Tuesday, Stoltenberg called on Russia to end its violation of Ukraine’s sovereignty. He said the alliance and Russia could not avoid having a relationship, but the real question is what sort of relationship that would be.

“NATO does not seek confrontation with Russia,” Stoltenberg said. “And nobody wants a new Cold War, 25 years since the fall of the Berlin Wall. But we cannot and will not compromise on the principles on which our alliance and the security of Europe and North America rest.”

The secretary-general also said in an interview with The Wall Street Journal that NATO has five times as many planes in the air conducting policing missions than it did a year ago.