The Ukrainian army is on high alert as pro-Russian fighters close in on the strategic port city of Mariupol.
Kyiv has accused Moscow of sending in troops to assist separatist rebels as they attempt to gain control of the city from the north and east.
Mariupol is of huge economic importance to Ukraine, it is a key import/export hub and the city contains two of the largest steelworks in Europe.
In Kramatorsk Ukrainian troops mobilised amid fears rebels will launch an attack on the city from its stronghold of Donetsk 100 kilometers to the south.
In Donetsk itself fighting continued overnight as government forces and rebels exchanged mortar fire.
Civilians caught in the crossfire are sheltering in basements.
In the village of Spartak a school where local people sort sanctuary came under attack.
As many as 3,000 people have been killed since the unrest began in April.