TOKYO (Kyodo) -- Japanese Prime Minister Sanae Takaichi on Thursday called Russian President Vladimir Putin's visit to an island in a Russian-held, Japanese-claimed island chain off Hokkaido "totally unacceptable."

Speaking to reporters in Tokyo, Takaichi said the Northern Territories are Japanese territory "historically and under international law" and that the trip by Putin to Etorofu Island earlier in the day had made efforts to restore relations with Russia more difficult.

She added that the government would carefully consider its response to the visit and urged Russia to take the gravity of the situation seriously.