Ukrainian President, Petro Poroshenko told "Tass" news agency, on Sunday that the cease-fire in eastern Ukraine has allowed the Ukrainian army to strengthen its positions. Poroshenko added that the silent period helped to strengthen the forces and restore combat readiness. He urged, at the same time on the need to make efforts to release the prisoners of war in the Christmas holiday. Moreover, Poroshenko has declared the cessation of hostilities on the fourth of December, which was welcomed by the Republics of Donetsk and Lugansk.