The central government says it will lodge a protest with Moscow after a senior political figure in the Kremlin paid an official visit to one of the Russian-held islands off Hokkaido on Wednesday.
Sergei Ivanov, chief of staff of the Presidential Executive Office and a close adviser to Russian President Vladimir Putin, inspected an airport on Etorofu that opened Monday.
The facility, located near Shana, known in Russia as Kurilsk, has a 2,300-meter-long runway and will serve both civilian and military flights.