ULAN-UDE, Russia (Kyodo) -- A Japanese man was seized by Russian border guards on Sunday for allegedly making an unauthorized visit to Kunashiri Island, one of the disputed islands off Hokkaido, sources familiar with the matter said Monday.
The man, Keisuke Kuriyama, born in 1974, was seized while on a rubber raft in the sea north of the island and transferred Monday to Furukamappu, called Yuzhno-Kurilsk in Russia, they said.
The Japanese man did not have a Russian visa. Russian authorities are studying how to pursue judiciary action against him, the sources said.
In Tokyo, State Foreign Secretary Yutaka Banno confirmed Monday the detention of Kuriyama by Russian authorities, saying the Russian border guards had informed the Japanese Consulate General in Yuzhno-Sakhalinsk on the matter earlier in the day.
The Japanese Foreign Ministry has urged the Russian Embassy in Tokyo to ensure Kuriyama's safety and release him soon, Banno said at a press conference.
Tokyo has also conveyed to Moscow its regret over the incident, as the detention of the man by Russian authorities in the disputed island runs counter to Japan's sovereignty claim to the territory, he added.
Some Japanese nationals have visited the disputed islands via Sakhalin Island with Russian visas. The former Soviet Union seized Kunashiri and three other islands off Hokkaido from Japan at the end of World War II.