Tokyo on Thursday moved quickly to reaffirm official policy calling for the return of four Russian-held islands off Hokkaido, a day after former Prime Minister Yoshiro Mori suggested a compromise that would leave one in Moscow's hands.

Chief Cabinet Secretary Yoshihide Suga reiterated the government's stance that all four islands — Etorofu, Kunashiri, Shikotan and the Habomai islets — must be returned.

Speaking on a TV news program Wednesday, Mori said the national border with Russia could be drawn north of Kunashiri Island, which would leave Etorofu — the largest of the four — in Russian territory.