Japanese former residents of Russian-controlled islands off Hokkaido flew to two of them on Sunday and visited their ancestors' graves, in the second such air trip negotiated during a decades-long spat over the islands' ownership.

A group of 70 people, including former residents of Kunashiri and Etorofu, their families and government officials, are scheduled to fly back to Japan's northernmost main island on Monday.

"It is bliss for me to console the souls of the many people buried in our hometown," Tadaaki Iwasaki, an 84-year-old former resident of Etorofu who heads the group, said Saturday ahead of Sunday's departure from Nakashibetsu airport.

The trip by air to Etorofu and Kunashiri was in line with an agreement between Prime Minister Shinzo Abe and Russian President Vladimir Putin in April 2017 to reduce the burden on the aging former islanders. The first air trip was made in September last year.

There had previously only been trips by chartered ships to the islands, seized by the former Soviet Union after Japan surrendered in World War II in August 1945.

The islands of Etorofu, Kunashiri, Shikotan and the Habomai islet group are collectively called the Northern Territories in Japan and the Southern Kurils in Russia. The territorial row has prevented Japan and Russia from concluding a postwar peace treaty.