The attacks in the eastern industrial belt near the Russian border underscored the difficulties of the embattled Kiev government in resolving a crisis that is threatening to tear the country apart.
Ukraine's Prime Minister Arseniy Yatsenyuk accused Russia of trying to "escalate the conflict" and disrupt today's vote, calling on the UN Security Council to hold an urgent meeting on the crisis.
He said the Kremlin's announcement of a troop withdrawal from the border was merely a "bluff", and that even if soldiers were redeploying, Ukraine was still being infiltrated by "armed terrorists".
Adding to the chaos in the east, armed separatists seized four coal mines in the first such confirmed attack on the main economic engines of the former Soviet republic.
Western governments have pressured Russia not to meddle in the snap election, seen as crucial to preventing all-out civil war erupting on Europe's eastern flank.
Russia set Western nerves on edge when it massed some 40,000 troops on the border, raising fears of an invasion into eastern Ukraine after its seizure of the Black Sea peninsula of Crimea in March.
Today, Russia's defence ministry said four trains and more than a dozen planes were taking troops and equipment away from the border in what President Vladimir Putin said were measures to create "favourable conditions" for Sunday's election.
NATO chief Anders Fogh Rasmussen said he had seen some evidence of limited Russian troop activity that he hoped was "the start of a full and genuine withdrawal".