Japan on Tuesday ordered a Russian diplomat based in Sapporo to leave the country within six days, Foreign Minister Yoshimasa Hayashi said, in retaliation for Moscow's expulsion of a Japanese consul last month.He said Tuesday that the Russian detention and interrogation of the Japanese consul was a "clear and serious violation" of international law and "extremely regrettable."Vice Foreign Minister Takeo Mori summoned Russian Ambassador to Japan Mikhail Galuzin to the ministry to inform Moscow of Tokyo's countermeasure, according to Hayashi.But Hayashi stopped short of giving details about the Russian diplomat, saying merely that Japan responded "accordingly" to Moscow's expulsion of the consul.Since Russia invaded Ukraine in late February, Japan's relations with the country have frozen, with Tokyo joining Western nations in imposing economic sanctions on Moscow."