A top NATO commander warned on Wednesday that "continual attacks" against Ukraine were hampering Kiev's efforts to modernise its army enough to one day join the Western military bloc.

The Cold War-era alliance's security chief Thrasyvoulos Terry Stamatopoulos made no direct reference to Russia -- a former superpower that flatly denies allegations it is orchestrating the conflict in order to halt Ukraine's march toward the West.

But he reaffirmed NATO's commitment to helping the ex-Soviet country both defend itself and build up an intimidating army that averts the possibility of future conflicts.

"We are well aware of the formidable challenges that Ukraine is facing," Stamatopoulos told a defence meeting in Kiev.

"It's not easy to launch wide-ranging reforms while managing a major conflict and deterring continual attacks against your territorial integrity," he said.

The assistance secretary general's visit to Kiev comes three months into a ceasefire that has managed to scale down but not halt the pro-Russian uprising that has claimed nearly 6,300 lives in Ukraine's industrial east.

Russian President Vladimir Putin rejects accusations his generals are fomenting the insurgency to weaken the pro-Western leadership that toppled a Moscow-backed president in February 2014.

The Kremlin hopes that the ceasefire's ability to stem the worst bloodshed will prompt the European Union to lift some of the more punishing sanctions against Russia in the next few months.

A first wave of punitive measures was  adopted in response to Russia's March 2014 seizure of Ukraine's Black Sea peninsula of Crimea.

Nations such as Greece and Cyprus -- their own economies in peril -- have balked at the idea of extending sanctions through the end of the year.

- Winning back Crimea -

The latest truce leaves parts of the Russian-speaking Lugansk and Donetsk regions in the east under the insurgents' control.

Some rebels now warn that they may try to push back government forces even further should President Petro Poroshenko fail to award them permanent semi-autonomous status.

State and local officials said the latest of what remain daily clashes claimed the lives of four civilians and one Ukrainian soldiers across the devastated war zone.

Poroshenko has thus far been unable to secure offensive weapons from his allies because of Western fears about Putin's potential response.

But he has pushed through legislation lifting Ukraine's neutral status and allowing the nation of 45 million to permanently host NATO troops.

Poroshenko on Wednesday also signed a new national security strategy focused on "restoring territorial integrity within the frameworks of the internationally-recognised borders of Ukraine".

The wording implies that Kiev still hopes to win back Crimea from Moscow despite Putin's decision to deploy new forces and weapons on the disputed peninsula.

The new security document also targets "Ukraine's integration with the European Union and creating the conditions necessary to join NATO".

Kiev hopes to receive an EU membership invitation by 2020 but has not targeted a NATO membership date.
Source: AFP