A former Japanese prime minister whose visit to Crimea brought harsh criticism at home says he's convinced that the referendum leading to the peninsula's annexation by Russia was legitimate.

Yukio Hatoyama's trip to Crimea this week was criticized both by the Japanese government and his own former party as contrary to Japan's denunciation of the Russian annexation, which occurred a year ago after a hastily called referendum on secession.

The referendum was held as Russian forces and Moscow-backed locals took control of Ukrainian military facilities and government buildings.

Hatoyama, who led Japan for eight months in 2009-10, said in Moscow Friday that from his Crimean trip "I was able to make sure by myself that the expression of popular will was free, peaceful and according to democratic regulations and procedures."