NATO's top military officer says Russia's large-scale air incursions into European airspace last week were intended to send the message that the country is still a "great power."

Gen. Phillip Breedlove says the flights were a concern because of their number and their provocative flight paths that took some of the aircraft as far as Portugal's Atlantic coast.

Breedlove told Pentagon reporters Monday that he believed the flights served a purpose. "My opinion is that they're messaging us," said Breedlove. "They're messaging us, you know, that they are a great power and that they have the ability to exert these kinds of influences in our thinking."

NATO there have been over 100 intercepts of Russian military air missions in 2014, a threefold increase from 2013. But while past Russian incursions have involved small numbers of aircraft, last week's flights were different in scope and reach.

"What you saw this past week was a larger, more complex formation of aircraft carrying out a little deeper," said Breedlove. "and I would say a little bit more provocative flight path."

NATO says the Russian flights are a safety concern because they normally do not go on established flight paths or turn on transponders that make them visible to civilian radars.

"It is a concern," said Breedlove. "These do not add to or contribute to a secure and stable situation, these kinds of demonstrations, and so they are problematic."

He praised NATO's swift response to the flights, "and the situation resolved as it always did, in a professional manner with professional intercepts by fully capable NATO defenders to escort the Russians while they were in the airspace."

Breedlove continued to voice concerns about large numbers of Russian troops still massed along Ukraine's eastern border. He estimated there are seven battalion task forces (between 800 and 1,000 in personnel) still arrayed along that border and between 250 and 300 Russian troops inside eastern Ukraine providing training and equipment to Russian separatists.

Fighting between those separatists and the Ukrainian military has continued in eastern Ukraine despite a ceasefire negotiated in early September.

Breedlove said the ceasefire has only served to "harden" the front lines between the Ukrainian military and Russian separatists "and much more softening of the actual Ukraine-Russia border."

"The Ukraine-Russia border is wide open in these spaces," said Breedlove. "It is porous, completely porous. Russian equipment, resupply, training flows back and forth freely across that interborder space."

Russian truck convoys with supplies for the separatists continue to flow into eastern Ukraine without Ukrainian permission, the most recent one being Sunday, he said.