Ukrainian Defense Minister Stepan Poltorak has claimed 7500 members of the Russian armed forces are present in his country, "preventing" Kiev from stabilizing the situation in the Donbass.

On Saturday Poltorak issued a statement reading that "unfortunately the stabilization of the situation in the east of Ukraine does not depend only on us."

The crisis-torn country is to boost its military's capabilities with "arms and equipment", UNIAN news agency quoted Poltorak as saying.

Kiev security forces earlier reported that unrest in Ukraine had claimed more lives, with four soldier killed and ten wounded during clashes with pro-Russian rebels.

Ukraine signed a ceasefire with self-proclaimed authorities at the Donetsk and Luhansk "People's Republics" in September, but the United Nations has repeatedly warned ever since that violence continues and nearly 1000 have lost their lives since the truce officially began.

The new coalition formed on Friday in Ukraine, with Prime Minister Arseniy Yatsenyuk remaning in office, declared it would set joining NATO as one of its priorities.

Russia is however determined not to allow Kiev's accession into the alliance.

Saturday's developments come as the US announced it had delivered three lightweight, counter-mortar radar systems to the Ukrainian armed forces.

The US State Department said it was planning to ship a total of 20 counter-mortar systems over the next several weeks.