Taiwan's leader Ma Ying-jeou on Friday visited an islet close to the Diaoyu Islands in the East China Sea, as Beijing said it is the "shared duty" of all the Chinese people across the Taiwan Straits to guard sovereignty.

Ma, amid escalating tension over the Diaoyu Islands, inspected the Pengchia Islet, which lies off northern Taiwan and is only about 140 kilometers west of the Diaoyu Islands, local media reported.

Japan has laid territorial claims over the islands, which belong to China. Japan has further strained its ties with China this year by a series of provocations concerning the issue.

Ma stressed that the waters off the Diaoyu Islands have traditionally been a fishing zone for Taiwan fishermen. He called for enhanced maritime patrols to protect maritime rights and interests in the waters off the islands.

"The Diaoyu Islands and affiliated islets have been China's inherent territory since ancient times, and it is the shared duty of all Chinese nationals, including those across the Straits, to safeguard the sovereignty of the Diaoyu Islands," Foreign Ministry spokesman Hong Lei said at a news conference in Beijing on Friday.

China-Japan ties have been strained since Shintaro Ishihara, the right-wing Tokyo governor, unveiled plans on behalf of the prefectural government to "buy" the islands in April.

Japanese Prime Minister Yoshihiko Noda, facing mounting nationalistic feelings and growing unpopularity over domestic policies, joined the bid and announced a plan in July to "nationalize" the islands, a move that prompted further protests from Beijing.

Reports on Wednesday said the Japanese government reached an agreement with the so-called private owner of the islands to pay 2.05 billion yen ($26.15 million) to buy three of the islands.

Tokyo is expected to hold a Cabinet meeting on Monday to officially affirm the final guidelines for "nationalizing" the Diaoyu Islands, unnamed sources told Japan's leading newspaper Yomiuri Shimbun on Friday.

Japanese media also said the deal will be finalized on Tuesday, a move that may spark further protests from China.

"The Japanese government is accelerating 'nationalization' in an attempt to block Ishihara's bid for the islands and to further beef up its rival claim over the islands," said Liu Jiangyong, an expert on Japanese studies and vice-dean of the Institute of Modern International Relations at Tsinghua University.

Liu said that Tokyo's so-called purchase of the islands will not change the fact that the Diaoyu Islands are the inherent territory of China.

Lu Yaodong, director of the department of Japanese diplomacy at the Institute of Japanese Studies under the Chinese Academy of Social Sciences, said Japan has not taken lessons from the recent anger of Chinese citizens over the matter.

On Aug 15, Chinese activists landed on one of the islands after sailing from Hong Kong. They were then illegally detained by Japanese authorities.

About a dozen Japanese right-wing activists raised their country's flag on the same island days later, prompting protests in cities across China.

Liu Yedan contributed to this story.

zhangyunbi@chinadaily.com.cn