Japan ordered a Russian consul in Sapporo to leave the country by October 10 in retaliation for the expulsion of a Japanese consul in Vladivostok last month, the foreign ministry said on Tuesday.

Japan’s decision comes after Russia’s FSB security agency said in September that it had detained the Japanese consul for suspected espionage and ordered him to leave the country.

Vice Foreign Minister Takeo Mori on Tuesday summoned Russian Ambassador Mikhail Galuzin and informed him of Japan’s decision. The country also declared the Russian consul in Sapporo “persona non grata” and demanded that the consul leaves Japan within six days.

“It is obvious that this latest step by the Japanese side can only lead to further deterioration of bilateral relations, which have already degraded recently as a result of Tokyo’s destructive policy,” Galuzin said in a statement.