Ukraine regrets a former Japanese prime minister's visit to Crimea and reserves the right to apply tougher measures to such "political tourists," Ukrainian Foreign Ministry spokesman Yevhen Perebyinis said.

"We regret former Japanese Prime Minister Yukio Hatoyama's trip to Russian-occupied Crimea. Ukraine understands that this unordinary and controversial Japanese politician is currently not a parliament member and does not occupy any official positions. We are also aware about his personal and family connections with Russia," Perebyinis said at a news briefing in Kyiv on Tuesday.

Ukraine highly values the Japanese government's position of not recognizing Crimea's annexation by Russia and practical steps toward supporting Ukraine's territorial integrity, Perebyinis said.

At the same time, Ukraine still believes such trips are unacceptable, he said.

Ukraine will not allow the subject of Ukraine's territorial integrity to be gambled on and "reserves the right to take tougher measures if such political tourists violate Ukrainian law," he said.

Hatoyama visited Crimea on March 10-12. He was reported to say that the purpose of his trip was to personally learn the Crimean residents' opinion regarding Crimea's accession to Russia.