Russia and Ukraine on Saturday began a long-awaited prisoner swap in a step that could ease bitter tensions over Moscow's annexation five years ago of the Crimea region.

While the unfolding exchange could help build confidence between Moscow and Kyiv — formerly Kiev — and allow them to start negotiating seriously on other issues, any road to a full rapprochement is likely to be long and complex.

After lengthy negotiations, expectations have been running high for the prisoner swap, which was described as imminent by the leaders of both countries in recent days.