Nato says it has observed a "significant" withdrawal of Russian troops from eastern Ukraine, but adds that some forces still remain there, reports GHN based on Ukrinform.
Lt Col Jay Janzen says it is difficult to determine the number of soldiers in Ukraine, as pro-Russian separatists control several border crossings.
Moscow denies arming the rebels and sending Russian troops to the Donetsk and Luhansk regions.
More than 3,200 people have been killed in clashes that erupted in April.
