While Russia pretends to retreat, Bataljon Vostok occupies Donetsk?

While Russia says it is retreating its troops...

Ukraine Border Security says no Russian troops in 10 km zone near the border, they've been withdrawn. @MFA_Ukraine says no movement. a mess
— Maxim Eristavi (@MaximEristavi) 20 mei 2014

Russian special forces 'Bataljon Vostok' enters Donetsk!!

#BREAKINGNEWS CLEARLY MARKED #GRU FORCES FROM "#BATTALION_VOSTOK" FROM #CHECHNYA INVADE DONETSK CITY! BRING BTR-70 pic.twitter.com/glrGIP74jk
— ConflictReporter (@MiddleEast_BRK) 20 mei 2014

So these guys just appeared at a roundabout in central Donetsk https://t.co/KP6Olsv7Qa
— Kevin Bishop (@bishopk) 20 mei 2014

You can read about Bataljon Vostok here, where it says it was disbanded in 2008!

Some question the importance of this appearance:

@MiddleEast_BRK It's from a chemical warfare mil unit BTR-70. Old decommissioned. Stop mumbling abt Russian coming in. THEY WON'T
— lennutrajektoor (@lennutrajektoor) 20 mei 2014

And so far only one BTR has been seen.

Also there seems to be some 'correction of the undisciplined' going on:

Tensions are very high between militias in Donbass now. Gorlovka crowd rolled into Donetsk and stormed local SBU for a 'commanders chat.'
— Andrew Roth (@ARothNYT) 20 mei 2014

Gorlovka militia has military trucks, sentries at either end of street. Nobody allowed through, Donetsk militia guy argued, lost and left.
— Andrew Roth (@ARothNYT) 20 mei 2014

Looks like criminal clashes between separatists "Donetsk Republic" gang and #Horlivka gang about to start near #Donetsk SBU, to be confirmed
— Ukraine Reporter (@StateOfUkraine) 20 mei 2014

So now some people think the rebels are fighting each other!

#Donetsk, situation becomes weird (unconf.): battalion Vostok fought against UA, now appeared to belong to #Akhmetov & is about to storm SBU
— Ukraine Reporter (@StateOfUkraine) 20 mei 2014

That the BTR belongs to Akhmetov seems unlikely.
The BTR has been seen more often in Donetsk already on the 17th of May:

#Donbass Location confirmed now. Self defense BTR-80 of "Vostok Battalion" in #Donetsk pic.twitter.com/x8EbmcWZGY #Ukraine
— Steiner (@Steiner1776) 17 mei 2014

Temporary conclusion should be: the gangs are restoring order within their own lines...

Gang war erupted in #Donetsk betwn horlivka & strelkov gangs. @ 16:00 #Donetsk #SBU HQ is surrounded by horlivka gang pic.twitter.com/3dMGlEvkZR
— lennutrajektoor (@lennutrajektoor) 20 mei 2014

In #Donetsk #SBU HQ strelok right hand #Abwehr is residing. That's why #Abwehr is in deep crap & summoned jurnos. pic.twitter.com/5MpRQGgqgI
— lennutrajektoor (@lennutrajektoor) 20 mei 2014

In this video at 16:30 the retreat of some forces in Donetsk can be seen. Mission accomplished?

Also read about Putins goals.