Ukraine's Joint Forces have tightened their control over several towns in eastern Ukraine while acting in compliance with the Minsk peace agreements, Chief of the General Staff of Ukraine's Armed Forces Viktor Muzhenko has said.

"The Ukrainian army strictly observes the Minsk agreements. We perform tasks within the framework of the Minsk agreements: we open fire only in response. This is about strengthening control over several settlements in the Joint Forces Operation zone," Muzhenko told journalists in Lviv region on Friday.

When asked to clarify which specific towns in the "grey zone" along the contact line in Donbas were retaken, Muzhenko said: "The village of Pivdenne, for example, the village of Oleksandrivka, and some other populated localities."

Yuriy Biriukov, an advisor to Ukraine's President Petro Poroshenko, earlier said on Pryamiy TV channel that Ukraine's Armed Forces control the entire "grey zone" along the contact line between Ukrainian government troops and Russia-occupation forces in Donbas.