Moscow (CNN) -- Russian Prime Minister Dmitry Medvedev visited islands claimed by both Russia and Japan on Tuesday, provoking an angry reaction from Tokyo.
He held a meeting with the governor of Sakhalin and visited Kunashir Island, which is near Japan's large northern island of Hokkaido.
Kunashir is one of the Kuril Islands, which Russia considers part of its Sakhalin region.
But Japan claims some of the islands as its territory.
Japanese Chief Cabinet Secretary Osamu Fujimura said Tuesday that Russia was taking the "wrong position" with the visit.
Russian Foreign Minister Sergey Lavrov said there was nothing to comment on when he was asked about the visit.
"The Russian prime minister was on a scheduled tour of his country," he said.
Lavrov said he hoped to meet his Japanese counterpart "very soon" to discuss cooperation between the countries "substantively and constructively."
Medvedev held talks with Sakhalin's governor on improving air transportation between islands, according to the Russian Federation's government website.
When he was president, Medvedev became the first Russian leader to visit the islands when he went there in November 2010.
The Kurils stretch between Russia in the north and Japan in the south. Following Japan's defeat in World War II in 1945, the Soviet Union annexed the four southernmost islands, which previously belonged to Japan.
Ever since, the islands -- called the South Kurils by Russia and the Northern Territories by Japan -- have been the subject of dispute. That dispute has prevented the two countries from signing a formal peace treaty following World War II.
CNN's Ben Brumfield and Alla Eshchenko contributed to this report.