Russia has significantly built up its military capabilities in Crimea since the peninsula was incorporated into its territory following a local referendum, NATO officials say.

The processes there "are easy to describe as militarization", NATO Supreme Allied Commander Europe Philip Breedlove has told Ukraine's 1+1 TV channel.

Gen Breedlove's claims come amid new Black Sea exercises being carried out by the alliance this week.
 
It also follows Russian President Vladimir Putin's revelations of Monday, in an interview he used to admit for the first time the reasons Moscow moved to overtake Crimea.

"The situation developed in such a way in Ukraine that we were forced to start work on returning Crimea into Russia. Because we cannot throw this territory and people living there to fend for themselves under nationalist command," RIA Novosti quotes Putin as telling Rossiya 1 channel.

This was the first publicly made statement showing the incorporation was planned well beforehand, and was not a spontaneous move as the President had previously suggested.

In Putin's words, an "indoor poll" was carried out in Crimea following the Maidan developments in Ukraine (and the overthrow of President Viktor Yanukovych) which showed 75 percent of its citizens wished to reunite with Russia.

"Then it was evident for me that if we carry this out, the share, or the number of those who would like to see this historical event happen would be much higher," Putin added.`

At the same time he stressed Moscow's actions were not tantamount to an "annexation", but an opportunity for Crimea citizens to voice their opinion:

"We acted as we were obliged to act."

He also admitted Moscow was prepared to conduct a rescue operation for Yanukovych and had been ready to help him out of Ukraine through "land, sea and air" action following the Maidan developments. It was during the planning phase of this operation that the Crimean move was decided, the Russian head of state argues.

Putin's interview was on the occasion of a documentary called Crimea. The Way Home, which is due later in 2015.