Kiev: Ukraine`s defence minister warned on Monday that a "great war" had broken out with Russia over his country`s future that could claim tens of thousands of lives.
"A great war has arrived at our doorstep -- the likes of which Europe has not seen since World War II. Unfortunately, the losses in such a war will be measured not in the hundreds but thousands and tens of thousands," Valeriy Geletey wrote in a Facebook post.
Russia on Monday again denied either sending or planning to send troops into eastern Ukraine to help separatist rebels pursue their recent counteroffensive against the pro-Western government`s forces.
But insurgency leaders have admitted that some off-duty Russian soldiers had already joined their ranks.
NATO has also accused the Kremlin of advancing more than a 1,000 soldiers and heavy weapons across the Ukrainian border in recent days.
Geletey wrote on Monday that "hundreds of Russian soldiers and officers have permanently entered Ukraine`s (eastern) `black earth` region."
But he stressed that "Ukraine has no plans to surrender" and compared the conflict to the "Great Patriotic War" -- the name former Soviet nations use for their fight against Nazi Germany in World War II.