With an Upper House election looming this weekend, the Japanese cabinet plans to strengthen territorial claims on hundreds of remote islands in the East China Sea, observers said.

Tokyo will "nationalize" some islands that have no private owners shortly after a survey of islands is completed in 2014, leading Japanese newspaper Yomiuri Shimbun quoted an unnamed government source as saying on Monday.

The Japanese government plans to establish a task force to research the ownership and names of around 400 islands, a move described by Agence France-Presse as an attempt to bolster Japan's territorial claims.

The latest move is designed to establish more reference points in territorial waters, and if the islands' ownership is unclear, the government will officially name and nationalize them, the newspaper reported.

Wu Hui, an international law expert at the University of International Relations in Beijing, said if part of these islands falls into the scope of territorial disputes, other countries may lodge serious protests.

"Moreover, a unilateral move to nationalize islands will raise questions over the legitimacy of such a move."

China-Japan relations were greatly damaged after Tokyo illegally nationalized part of China's Diaoyu Islands in the East China Sea in September.

As far as Tokyo is concerned, nationalizing controversial remote islands is part of legislative preparations for further claims, Wu said.

The island survey was announced shortly after the Japanese defense authorities indicated that they may "guard and retake" remote islands, analysts said.

The Japanese Defense Ministry is proposing "boosting the marine functions of the Self-Defense Forces" in its interim report for a planned revision of the country's long-term defense policy, Japan's Kyodo News Agency reported on Sunday.

The move underscores the importance attached by the ministry to strengthening the Self-Defense Forces' ability to defend remote islands, Kyodo said.

Li Guoqiang, deputy director of the Center for Chinese Borderland History and Geography at the Chinese Academy of Social Sciences, said, "Tokyo is now attempting greater control of maritime areas in order to give it an advantage in territorial disputes.

"Japan is seeking to be a political and military power with its moves on maritime disputes and its so-called measures to secure maritime interests," Li said.

In mid-June, the Japanese armed forces participated in a joint military drill with the US Army, which involved the simulated retaking an airport occupied by an "enemy".

These moves highlight Tokyo's "desperation" to defend and retake remote islands at an early date, said major Japanese newspaper Asahi Shimbun.

Japanese Prime Minister Shinzo Abe is expected to visit Okinawa Prefecture in the southwest of the country on Tuesday.

The trip seems to demonstrate his determination to enhance the defense of remote islands amid the flaring up of tension with China, Japan's Sankei Shimbun newspaper said.

"It is rare for a prime minister to visit remote islands during an election campaign," Japan's Jiji Press News Agency commented.

Mo Jingxi and AFP contributed to this story.