Russia detained a Japanese diplomat accused of being caught 'red-handed' trying to buy state secrets and for spying on a 'country in the Asia-Pacific region'.

Motoki Tatsunori, the Japanese Consul General in Vladivostok, was arrested for allegedly soliciting 'restricted' information about an unnamed country in the Asia-Pacific region - which is speculated to be China.

The FSB, the KGB´s successor agency, released a statement about the matter, accusing Tatsunori of gathering secret information on Russia and ordered him to leave the country within 48 hours.

The statement said: '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 also accused the diplomat of seeking out information on 'the impact of Western sanctions' on the surrounding Primoriye region, according to news agencies.

The FSB said it had lodged a protest with Tokyo through diplomatic channels and Russia's foreign ministry said Tatsunori had been declared persona non grata and ordered to leave the country within 48 hours.

The Kremlin has repeatedly referred to Japan as a 'hostile' country, a designation it shares with the US, EU countries and their Western allies, since Tokyo joined them in slapping sanctions on Moscow after Russian troops entered Ukraine on February 24.

Japanese authorities have not yet commented on the incident.