"In a number of units, officers of the Russian armed forces who arrived from Russia provided a 100% replacement," the statement reads.

“The officers who were replaced are being sent back to Russia," reads the message.

Read alsoUkraine reports 2 WIAs amid 65 enemy attacks in last dayAt the same time, according to the IR, at the end of 2016, Russian officers in Donbas were informed that their deployment will last at least until the end of 2017.

"The reason for the emergency rotation of advisers and instructors is currently unknown," Tymchuk said.