"We drew attention to the publication of the Kyodo news agency with reference to materials from the former archive of the Central Committee of the CPSU," RIA Novosti reports.
The Russian Foreign Ministry noted that studying and commenting on written sources of past years is the prerogative of historians, "especially if we are talking about some private opinions or estimates of a presumptive nature."
The ministry added that, within the framework of a bilateral dialogue with Japan, the USSR Ministry of Foreign Affairs, and subsequently the Russian Foreign Ministry, "consistently promoted a position well known to everyone: the South Kuriles became part of our country legally following the results of World War II, and Russian sovereignty over them is undeniable."
Earlier, Russian President Vladimir Putin said that Russia wants and will develop relations with Japan, but will do so only in accordance with the main Russian law.