Russian President Dmitry Medvedev visits a young family during his visit to Kunashir one of the Kuril islands Photo: EPA Mr Medvedev ignored Japanese pleas to stay away and became the first Russian leader since the fall of the Soviet Union to visit the disputed territory that the Russians call the Kuril Islands and the Japanese the Northern Territories.
The question of who owns the islands, which were seized by Soviet troops at the end of the Second World War, is so bitter that Russia and Japan have yet to formally sign a post-war peace treaty sixty five years after hostilities ended.
Japan reacted with fury and said it still wanted the islands back. Naoto Kan, the Japanese prime minister, said the visit was "very regrettable".
In a measure of how seriously Tokyo was taking the matter, it summoned Russia's ambassador to Japan for an explanation.
The Kremlin in response summoned Japan's ambassador to Moscow in retaliation, professing itself baffled by such a strong Japanese reaction.
"The reaction of the Japanese side to President Medvedev's visit to the Kurils is unacceptable," said Sergei Lavrov, the Russian foreign minister. "This is our land, and the Russian President is visiting Russian land," he added, signalling there was no room for compromise.
Mr Medvedev spent four hours on one of the four islands that Tokyo wants back visiting a power plant, a kindergarten and a fish processing plant. But the diplomatic fallout from his visit is likely to reverberate for much longer.
The row comes as Mr Medvedev prepares to attend a meeting of the Asia-Pacific Economic Cooperation organisation in Japan later this month.
The timing of his historic visit to the contested islands was particularly sensitive for Japan. Tokyo is only just recovering from a diplomatic spat with China over a group of disputed islands in the East China Sea that saw Japan detain and then release the captain of a Chinese fishing boat under massive pressure from Beijing.
