TOKYO: Tokyo said Tuesday it was "extremely regrettable" that its diplomats had been unable to visit a Japanese journalist detained in Russia, despite a bilateral protocol that guarantees the right to consular access.
Russia arrested the journalist from the Hokkaido Shimbun newspaper on the Far East island of Sakhalin a week ago on suspicion of espionage.
Moscow has arrested several citizens of what it calls "unfriendly" countries in recent years, accusing them of working for Western intelligence services.
Japan has denied the spying allegation and demanded that Russia release the man.
Chief cabinet secretary Minoru Kihara said the protocol, which was signed between Japan and the Soviet Union and remains effective with Russia, ensures the right to consular access within "a period of no later than four days from the time of arrest or detention".
"It is therefore extremely regrettable that, despite this provision, a consular visit was not realised within the prescribed period," Kihara said.
Japan will "continue to strongly urge the Russian side to arrange a consular visit at the earliest possible time", he said, adding that Tokyo was also demanding his release, humanitarian consideration, and fair treatment.
Russian media reported that the journalist would remain in custody until Dec 12.
Moscow's foreign ministry last week identified the arrested reporter as Yuki Imai, with a spokeswoman saying he was accused of "conducting espionage activities on Russian territory".
Russia's FSB security service said a Japanese national was arrested on Sakhalin - near a disputed cluster of islands - but did not name the individual.
It said the person had worked for Japanese intelligence to collect information about Russia's defences.
Japanese prime minister Sanae Takaichi denied the spying claim, saying "there is no such fact".
Tokyo summoned Russian ambassador Nikolay Nozdrev to lodge a protest over the arrest.
Moscow and Tokyo have been locked in a territorial dispute for decades over the status of a string of islands off the northeast coast of Japan and to the southwest of Russia's Sakhalin region.
The Kuril Islands - called the Northern Territories in Japan - have been under Russia's control since the end of World War II, when they were seized by the Soviet Union.