Ukraine's army did not specify the location of the attack, saying only that one soldier "suffered fatal injuries" and another was wounded in the shelling.

Nine Ukrainian soldiers have died since the beginning of the year, with six of them killed in intensifying clashes over the past four days, according to an AFP tally based on official sources.

Rebel leaders have only claimed casualties among civilians but not their fighters.

Russian President Vladimir Putin on Monday recognised the independence of Ukraine's two separatist regions, approving deployment of regular troops into the region.

US and NATO official say Russia is now poised to invade Ukraine after surrounding it with 150,000 soldiers and then staging a series of military drills, including with its ally Belarus.

But Putin has not said when he might dispatch his force, saying on Tuesday that it would "depend on the situation on the ground".