Putin told reporters earlier today that the heavily armed men who took over Ukrainian military and political institutions in Crimea are not Russian soldiers, but rather local self-defense forces. This one picture proves that he is full of crap (as if we didn't already know that):
This is a picture of one of the "unidentified" self-defense soldiers standing in front of the Crimean Parliament Building in Simferopol, Ukraine. See that gun the soldier in the middle is carrying? That is an AS Val.
The AS Val is an integrally suppressed assault rifle, and uses a special subsonic 9x39mm round that is able to penetrate 6mm of steel at 200 meters. This lethal combination of stealth and power makes it an incredibly effective weapon for covert operations such as this one. It is heavily related to the VSS Vintorez sniper rifle that has also been seen in Crimea (see the soldier on the right below).
Most importantly, the AS Val (the Vintorez as well) is used exclusively by Russian Special Forces such as the Spetsnaz, MVD, and FSB and select Russian Army units. It is highly unlikely that a local militia or defense group could obtain an AS Val, because the Russians have keep this special weapon close to their chest; it has not been exported like the AK series of weapons. Sure, you may be able to get uniforms and gear, but no local militia would ever get an AS Val without direct Russian involvement.
In conclusion, those men were definitely Russians. And Putin, the next time you want to pull off a large scale operation like this and peg it on "local defense forces," give your men some weapons that allow for plausible deniability. You're not fooling anyone.
I mean, that's what America does.