The Ukrainian army has enlisted 86,000 servicemen by contract since early 2016, thus forming reserves, Ukrainian Defense Minister Stepan Poltorak said.

"A total of 86,000 servicemen were enlisted by contract during 2016 and early 2017, signifying a shift to the professional army. Contract servicemen are motivated, trained and battle-hardened people. Mobilization has stopped as a result," the minister said at a graduation ceremony at the Chernyakhovsky National Defense University on Friday.

Reserves have been formed thanks to the large number of servicemen enlisted by contract, Poltorak said.

"We have formed 100,000-strong reserves that may join the ranks within days. They are drilled each year," the minister said.

"We should be prepared for a change in the situation," he said.