TOKYO (AFP) - Japanese Prime Minister Shinzo Abe on Thursday congratulated Mr Xi Jinping for officially becoming China's president, as the two nations are locked in a row over an island chain, a senior Tokyo official said.

Japan wants to work with Mr Xi in the spirit of a "mutually beneficial relationship based on common strategic interests", Chief Cabinet Secretary Yoshihide Suga told a regular briefing.

"The Japanese government congratulates President Xi Jinping and the newly chosen leadership," Mr Suga said.

"The relationship with China is one of the most important international relationships for Japan," he said, adding that Mr Abe sent a congratulatory message to Mr Xi.

While Japan will not budge on its claim over Tokyo-administered islands in the East China Sea, called the Senkakus in Japan and claimed as the Diaoyus by China, Tokyo wished to work with Mr Xi from a big-picture point of view, he added.

"We have always kept our door open for dialogue with China," Mr Suga said.

Japan's relations with China, its biggest trade partner, have fallen to historic lows since Tokyo nationalised the islands last year, sparking violent street demonstrations across China.

For months, China has routinely sent ships inside the islands' territorial waters, sparking tense standoffs with Japanese coastguard vessels.