KIEV (AFP) - Ukraine's defence minister warned on Monday that a "great war" has 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," Mr Valeriy Geletey wrote in a Facebook post.