Japanese Foreign Minister Toshimitsu Motegi stated that Tokyo considers this territory to be part of Japan, both historically and under international law, stressing that the Japanese government "strongly protests" against Putin's visit.
The islands, known in Japan as the Northern Territories, are administered by Russia and are at the center of a decades-long territorial dispute. The issue has been one of the main obstacles to the signing of a peace treaty between Moscow and Tokyo after World War II.
During his visit to Iturup, Putin met with locals and tried local products, while Russian state media presented the visit as part of the development of the region.
The islands are also of great strategic importance to Russia. Iturup serves as one of the main Russian military air bases in the area.
Tensions have also been heightened by military activity. Last month, Russian and Chinese warships conducted a joint patrol in waters near the Kuril Islands, while Russia has previously conducted military exercises in the area, actions that have sparked protests from Tokyo.
