Yoshihiko Noda retained his post as Japanese prime minister after winning re-election to the presidency of his ruling Democratic Party of Japan, but questions remain about the sincerity of his promise to heal shaky China-Japan ties.

According to initial results, Noda got 818 points out of 1,231.

The prime minister was trailed by former Internal Affairs Minister Kazuhiro Haraguchi with 154 points, former Agriculture Minister Hirotaka Akamatsu, 123, and another former Agriculture Minister Michihiko Kano, 113.

Japanese Prime Minister and ruling Democratic Party of Japan leader Yoshihiko Noda casts his ballot during his party's presidential election in Tokyo on Friday. [Photo/AFP]

Yet Japan faces a diplomatic standoff with China after the Noda Cabinet on Sept 11 finalized an illegal "purchase" of the Diaoyu Islands, which have belonged to China for centuries.

Beijing lodged bitter protests to Tokyo later and took a series of countermeasures to reaffirm sovereignty over the uninhabited islands in the East China Sea.

More than a dozen patrol ships from the Chinese mainland, including marine surveillance vessels and fishery administration boats, continued their patrols in the waters off the islands on Friday, the Japanese coast guard told media.

Safeguarding China's sovereignty over the Diaoyu Islands, as well as its national marine rights and interests, will be a "long-term and critical struggle", Chen Lianzeng, deputy director of the State Oceanic Administration, said at a Thursday symposium on protecting the islands.

A protest ship from Taiwan arrived in the waters surrounding the islands and was spotted 44 kilometers off one of them. Banners reading "Protect Diaoyu" and "Get back Diaoyu" in Chinese were seen on board.

A thematic map of the islands, issued on Tuesday by SinoMaps Press to inform the Chinese public about the country's sovereignty over them, has been a hit in bookstores nationwide, with an initial circulation of 50,000 copies. The printing office is rushing to make more copies.

The bitter spat between the two neighbors has also led to a spate of canceled, suspended or delayed ceremonies, which were intended to commemorate the 40th anniversary of the countries' normalization of diplomatic relations in 1972.

"The blame lies entirely with Japan," Foreign Ministry spokesman Hong Lei told a daily news conference on Friday, and he reiterated Beijing's urge for Tokyo to make damage control and get back to negotiations for a resolution of the dispute.

In an effort to diminish the tension between Japan and China, Noda said on a Japanese television program late on Thursday he is cautiously optimistic about talks with Chinese leaders on the sidelines of an upcoming UN meeting.

When meeting with reporters after winning the election on Friday, Noda said he is scheduled to fly to New York on Monday to attend the United Nations General Assembly meeting.

Yet Noda will use the occasion to appeal to the international community in a speech calling for territorial matters to be resolved in accordance with the principle of "rule of law" amid souring relations with both South Korea and China.

Noda's speech on the islands dispute may be given on Wednesday, according to Japan's Mainichi Shimbun newspaper.

Observers said Noda made conflicting remarks when he vowed to send envoys to China for talks while sticking to Japan's stance of denying the existence of an islands issue.

Liu Jiangyong, an expert on Japanese studies and the deputy dean of the Institute of Modern International Relations at Tsinghua University, said Noda's call for dialogue may be a "stalling tactic to gain time", and little hope is evident between the sides to eliminate differences on principal issues.

Leaders of both countries agreed in the 1970s to put aside the islands dispute to pave the way for normalizing ties.

Noda is now also facing mounting pressure from powerful domestic economic tycoons who are criticizing him for damaging Japan-China ties.

Liu Yedan, Xinhua and AFP contributed to this story.

zhangyunbi@chinadaily.com.cn