Japan on Tuesday demanded Russia apologize for detaining a diplomat over alleged espionage, denying the charge and accusing Moscow of blindfolding and pinning the man down in "unbelievable acts."
The Japanese diplomat based in the eastern city of Vladivostok was deemed "persona non grata over illegal intelligence activities", top government spokesman Hirokazu Matsuno told reporters, citing the Russian foreign ministry.
"The official was blindfolded, with pressure applied to both his hands and head so he was unable to move while being detained, and then he was questioned in an overbearing way," Matsuno said.
Japan "strongly protests these unbelievable acts", he said, denying the espionage allegations.
The diplomat has been released and will leave Russia by Wednesday, he added.
Japan summoned the Russian ambassador and "demanded a formal apology" for the treatment of the diplomat, which Matsuno said violated the Vienna Convention on Consular Relations.
Russia said Monday that it had detained a Japanese consulate official based in the eastern city of Vladivostok for soliciting "restricted" information, according to Russian news agencies.
"A Japanese diplomat was detained red-handed while receiving, in exchange for financial reward, restricted information about Russia's cooperation with another country in the Asia-Pacific region," the FSB, the KGB's successor agency, was cited as saying through its press service, without specifying the third country.
The FSB identified the official as Tatsunori Motoki, accusing him of seeking out information on "the impact of Western sanctions" on the surrounding Primoriye region, according to news agencies.
The FSB distributed a short video it said showed the diplomat acknowledging that he had violated Russian laws, and reportedly said Moscow had lodged a protest with Tokyo through diplomatic channels.
Russia considers Japan to be a "hostile" country -- a designation it shares with all European Union countries, the United States and its allies, including Britain and Australia.
Tokyo had complex relations with Moscow before the invasion of Ukraine in February, and the two sides have yet to sign a post-World War II peace treaty.
Attempts to do so have been hampered by a long-running dispute over islands controlled by Russia, which calls them the Kurils.
In its latest sanctions, Japan's government on Monday banned the export of materials that may be used for chemical weapons to 21 Russian organizations, including science laboratories. The measure was approved by the Cabinet following a decision by Group of Seven foreign ministers last week.
The Associated Press contributed to this report.
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