Russia has opposed to Montenegro's NATO membership. Moscow said it was another case of the alliance's encroachment and military build-up in the Balkans.

The Russian Foreign Minister Sergey Lavrov has said in the past that he believes this is an artificial membership, saying that this decision should have been put to a referendum.

Now the spokesperson to the foreign minister goes even further, saying this is a humiliation for the people of Montenegro, adding the bombardment from NATO some 17 years ago in the region, saying this is even a case of Stockholm Syndrome.

The real threat and real issue comes from the increasing presence of the US, increasing presence from NATO in Europe's east flank. This is the start of some arm race NATO and the US is trying to engage with. That's a certain concern for Moscow on their watch.