Japanese Foreign Minister Seiji Maehara on Monday summoned Russian ambassador to lodge a protest against Russian President Dmitry Medvedev's visit to disputed Kunashiri Island, Kyodo News reported.

The Russian envoy, however, insisted that the president's visit is Russia's domestic issue, according to the report.

Earlier in the day, Maehara noted at a meeting of the budget committee of the lower house that Medvedev's visit to the disputed isle "hurts Japanese public sentiment."

Also at the meeting, Prime Minister Naoto Kan asserted that the islands are Japanese territory and described Russian president's move as "extremely deplorable," while Chief Cabinet Secretary Yoshito Sengoku said that Japan is to decide what steps it will take after checking the president's remarks.

Local media reported that Medvedev visited Kunashiri Island early Monday. He has thus become the first leader from Russia or the former Soviet Union to set foot on any of the islands off Hokkaido, which are called the Northern Territories in Japan and the Southern Kurils in Russia.