Ukraine on Monday reported repelling a rare tank assault by pro-Russian rebels that threatened to usher in a dangerous escalation to the 16-month war.

President Petro Poroshenko said about "200 insurgents used tanks to storm" Novolaspa -- a village half-way between the separatists' de facto capital Donetsk and the Kiev-held port of Mariupol -- in a pre-dawn raid that caught government soldiers off guard.

Chief of Staff General Viktor Muzhenko "informed the president that the Ukrainian forces gave a fitting rebuff and repelled all the attacks", the presidency said.

"Ukrainian forces are in full control of the situation," it added.

The Ukrainian foreign ministry called the incident "a dangerous indication of a further escalation to come".

But the rebels denied advancing their forces and signalled that they had always had militia units stationed in Novolaspa.

"The armed forces of Ukraine simply put the village under a heavy shelling attack," a local separatist official told the rebels' main news site.

"Novolaspa remains under the control of the People's Republic of Donetsk."

Kiev on Monday reported the death of one soldier while the insurgents accused government forces of killing a civilian in the rebel-held bastion of Gorlivka.

Poroshenko subsequently called in the head of Ukraine's national security service and defence minister along with the top army general to forge a response to "the rise in the number of attacks, particularly those using artillery fire, by the Russian-terrorist forces", his office said.

Kiev refers to its eastern campaign as an "anti-terrorist operation" designed to quash a revolt devised by the Kremlin and backed by Russian troops -- a charge Moscow resolutely denies.

The two self-proclaimed republics of Donetsk and Lugansk launched their revolt shortly after the February 2014 ouster of a Moscow-backed president and Russia's subsequent seizure of Ukraine's Crimea peninsula.

The clashes have killed more than 6,800 people and sent Moscow's relations with the West crashing to their lowest point since the cold war.

It has also caused a humanitarian crisis that left 1.4 million homeless and sent Ukraine's economy -- heavily dependent on exports from the industrial east -- into a tailspin.

The West is still pinning hope on a February truce agreement that has often been ignored but also kept the fighting limited to individual flashpoints along the Russian-speaking east of the former Soviet state.

The latest reported clashes came one day after a special monitoring mission from the Organization for Security and Co-operation in Europe saw several of its armoured vehicles torched outside its headquarters in Donetsk.