The United States has spotted some Russian troop movements near the Ukraine border but no sign of a large-scale withdrawal, U.S. Army Secretary John McHugh said on Wednesday.

"What we know thus far is that there has been certain troop movements, but I have received no confirmation, either through Pentagon sources or NATO sources, that there has been a wholesale repositioning of those troops off the border," McHugh told a news conference during a visit to Estonia.

Russia's state-run RIA news agency quoted the Defence Ministry earlier as saying Russian troops that took part in military exercises in three provinces bordering Ukraine had packed up and were preparing to return to their permanent bases.