Russian Prime Minister Dmitry Medvedev arrived at Kunashir islet in the Far East on Tuesday on his second visit to the disputed Southern Kuril archipelago, sparking protests from Tokyo.

After arriving at Mendeleyevo Airport on Kunashir, Medvedev visited a deep-water dock and a fish-packing plant in Yuzhno-Kurilsk port, the administrative center of the Southern Kuril City District.

Medvedev had earlier said he would visit national projects under construction on the islands and meet local people.

He said the visit was "extremely important" and the new government would continue visiting the Southern Kurils.

As expected, Medvedev's visit raised hackles in Japan.

The Japanese Foreign Ministry summoned later on Tuesday the Russian ambassador Yevgeny Afanasyev and expressed Tokyo's "extreme regret" in a statement.

"Kunashiri Island is an integral part of Japanese territory and the Japanese government can hardly accept such a visit," Vice-Foreign Minister Kenichiro Sasae said in a statement.

"The visit is not compatible with our country's position over the Northern Territories, and I take it as something that throws cold water on efforts to build a positive atmosphere in the Japan-Russia relations," said Japanese Foreign Minister Koichiro Gemba.

The visit took place just weeks after Japanese Prime Minister Yoshihiko Noda and Russian President Vladimir Putin agreed to reactivate talks on the territorial dispute.

Fyodor Lukyanov, editor of Russia in Global Affairs, expressed bewilderment at the purpose of the visit.

"It is unclear why this is needed now that the Japanese government is signaling that it would like to improve ties with Russia," he said. "This looks like window-dressing because little is being done for the Kurils right now."

Medvedev became the first Russian leader to visit the chain in November 2010 - when he still held the post of president - sparked a furious reaction from Tokyo which condemned the trip as a "unforgivable outrage".

The disputed isles, known as Etorofu, Kunashiri, Shikotan and the Habomai islet group in Japan, were seized by the Soviet Union following Japan's surrender in World War II.

Russia in 2005 suggested it would cede two of the islands if Japan gave up its claim to the other two, but Japan rejected the idea.

Xinhua - AFP - Reuters