The latest casualties across the Russian-speaking Donetsk and Lugansk regions came two days ahead of the planned start of a ceasefire aimed at winding down one of Europe's deadliest conflicts in decades.
The United Nations believes the eight-month uprising in eastern Ukraine has killed more than 4,300 people and driven nearly a million more from their homes.
It has also paralysed much of Ukraine's industry and left the nation of 45 million dependent on tens of billions of dollars in emergency global aid.
Charges of Kremlin backing for the insurgents have eroded much of the trust built between Moscow and the West in the post-Cold War era and left Russian President Vladimir Putin more isolated than ever in his dominant 15-year rule.
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The West fears the Russian strongman is trying to create a "frozen conflict" that keeps the Ukrainian leadership off-balance and continually dependent on Moscow.
Russia's violation of "the territorial integrity and sovereignty of Ukraine must not be allowed to stand," German Chancellor Angela Merkel told Die Welt newspaper.
The pro-Russian revolt erupted weeks after the February ouster in Kiev of a Kremlin-backed president who had ditched a landmark EU pact that would have paved the way to Ukraine's membership in the 28-nation bloc.
The Kremlin flatly denies the charges and accuses Washington of orchestrating last winter's pro-European protests in Kiev and across more nationalistic parts of western Ukraine.
Putin this week said Ukraine will eventually regret the episode and realise the mistake it made when it finally ratified the EU deal three months ago.