MOSCOW - RUSSIA on Thursday condemned as unacceptable a law adopted by the Japanese parliament asserting sovereignty over four islands at the centre of a decades-long territorial dispute.

The row over the Pacific islands - controlled by Moscow since they were seized by Soviet troops in 1945 - has long held up the signing of a peace treaty between the two sides formally ending World War II.

'We consider the adopting of unfounded territorial demands towards Russia as inappropriate, unacceptable and in contradiction to the search for mutually acceptable decisions on a peace agreement,' said Russian foreign ministry spokesman Andrei Nesterenko.

The four islets north of Japan's Hokkaido island are called the Southern Kurils by Russia and the Northern Territories by Japan.

A law describing the islands as an 'integral part' of Japan was unanimously passed by the opposition-controlled upper house Friday after the lower house also approved it in May.

The foreign ministry's angry reaction came as Japanese Prime Minister Taro Aso met Russian President Dmitry Medvedev on the sidelines of a Group of Eight summit in Italy, their second meeting this year.

No breakthroughs on the issue were achieved at Mr Medvedev's last meeting with Mr Aso or in talks Mr Aso held with Russian Prime Minister Vladimir Putin in May. -- AFP