These chaps are the FC Chernomorets Odessa ultras, in sparkling form.
Given that the various ultra firms across Ukraine put aside their private wars to unite in favour of pro-Maidan forces in February, I wondered if they had anything to do with the events in Odessa on Friday. The interesting point about this was that it involved fans from all over Ukraine, from Karpathy Liviv to Shaktar Donetsk. There was some disagreement about what Ukraine should actually do, but all lined up on the anti-Yanukovych side.
Anyway, turns out the ultras were heavily involved and not just the locals either. Per this NYT report, the incident which culminated with the lethal firebombing of the local Trade Union headquarters that night started out as a joint rally in support of Kiev by ultras from Chernomorets and Metalist Kharkov. They were ambushed by anti-Maidan forces in a pattern that has become common in areas which antimaidan forces wish to exert control. But on this occasion the ultra forces chased the antimaidan crowd across town into the Trade Union headquarters and, after a brief seige, apparently burned it down, killing dozens.
A month or so earlier, Futbolgrad reported on the situation in Crimea, where pro-Russian sentiment is stronger. The local ultras there, too, combined to support Kiev, but this time got smothered by much more powerful local forces. The considerable numbers of Russian special forces present there undoubtedly helped, too. Likewise, in Donetsk, the Shakhtar ultras haven't felt able to do much more than offer verbal defiance in the face of the actual balance of power.
Given the apparent complete lack of interest by local law enforcement in establishing any kind of public order in contested parts of the country, and with the army apparently concentrating on Slavyansk, the success or failure of ultra manifestations gives us a workable rough guide to actually existing Ukraine. Kyiv rules, sort of, where they can put sufficient numbers on to the streets. But not beyond.