http://www.centerkor-ua.org/novosti/item/1251-polsha-vstupaet-v-vojnu-na-ukraine.html
A quick translation:
A barge was unloaded last night (between 3 and 5 am) in the port of Odessa, in an atmosphere of high secrecy, twelve supposedly self-propelled wheeled guns - 152mm gun-howitzer vz. 77 "Dana" of Czech production, that are serving as the armament of the Polish Armed Forces, as well as two staff buses and trucks. After unloading the artillery battalion (perhaps from the Mazury First Artillery Brigade), fully stocked Polish soldiers, continued under its own power to the railway station Razdel'naja for loading.
Military experts familiar with the situation suggest that this is the "unpleasant surprise for the militia", which Poroshenko mentioned earlier.
With the entry into open civil war in Ukraine of regular army of a foreign country - a member of NATO, the military-political situation changed radically. And fully unties the hands of the Russian Federation and its allies for an adequate response.
I can only add that during the civil war of 1917-1920 Polish interventionist army were also marauding the Ukrainian and Russian land and went as far as Moscow, until they got chased all the way to Warsaw. Looks like they are eager for a replay.