Ukrainian military forces have successfully established positions on the eastern side of the Dnieper River, according to a new analysis, giving rise to speculation Sunday that the advances could be an early sign of Kyiv's long-awaited spring counteroffensive.

The Institute for the Study of War, a Washington-based think tank, reported late Saturday that geolocated footage from pro-Kremlin military bloggers indicated that Ukrainian troops had established a foothold near the town of Oleshky, along with "stable supply lines" to their positions.