Several shots were heard Monday evening from the key East Ukraine airfield of Kramatorsk which Kiev said has been retaken from pro-Russian separatists in what it calls a “anti-terrorist operation” around Donetsk. The casualties are not confirmed by the separatists. Ukrainian Air Force jets were seen over the airfield. Pro-Russian activists have seized police buildings in nearly a dozen towns. Kiev also claims its operation is going on in Slaviansk. Moscow has warned Kiev not to go through with armed action against the pro-Russian regions of the east. Both Moscow and Washington have urged restraint in the crisis with a quadrilateral conference in Geneva scheduled for Thursday between the US, Russia, the EU and Ukrainians. A pro-Russian source in Donetsk said Kramatorsk airfield was not taken by Ukrainian army or air force but a faction called the “Right Sector" and foreign mercenaries.