Japanese Foreign Ministry has lodged an official protest against the visit of a Russian high-ranking delegation to the disputed Kuril islands, Japan's Yomiuri newspaper said on Monday, RIA Novosti reported.
The Russian delegation led by Deputy Prime Minster Sergei Ivanov visited the island of Kunashir and Iturup on Sunday as part of a working tour around Russia's Far East.
The delegation included Minister of Transport Igor Levitin, Minister of Economic Development Elvira Nabiullina, Minister of Natural Resources Yuri Trutnev, Minister of Regional Development Viktor Basargin, and governor of the Sakhalin region Alexander Khoroshavin.
"The Japanese government considers this visit unacceptable and regretful," Yomiury said quoting an unidentified Japanese diplomat.
The protest has been delivered over the phone to Russian Ambassador in Japan Mikhail Bely, the paper said.
Both Japan and Russia have laid claims to the South Kuril Islands, called the Northern Territories by the Japanese, since they were annexed by the Soviet Union at the end of World War II. The dispute has prevented the two countries from signing a peace treaty to formally end hostilities.