Meanwhile, both sides in the conflict on June 19 accused the other of violating a cease-fire under the Minsk peace agreements by firing mortar and heavy artillery.

Since April 2014, more than 13,000 people have been killed in fighting between Kyiv's forces and the Russia-backed separatists who control parts of the eastern regions of Donetsk and Luhansk.

The cease-fire deals announced as part of the Minsk accords -- September 2014 and February 2015 pacts aimed at resolving the conflict -- have contributed to a decrease in fighting but have failed to hold.

With reporting by TASS