Japan is considering buying a chain of islands at the centre of a bitter territorial dispute with China and Taiwan, Prime Minister Yoshihiko Noda said Saturday, sparking an angry response from Beijing.
The islands in the East China Sea are called Senkaku in Japanese and Diaoyu in Chinese.
"There is no question that the Senkakus are an integral part of our country's territory in terms of history and international law," Noda told reporters.
"There exists no territorial issue or ownership issue as Japan is in effective control of the islands.
"From the viewpoint of how to maintain and manage the Senkakus in a calm and stable manner, we are making comprehensive studies on the matter by keeping in touch with the owner."
Chinese foreign ministry spokesman Liu Weimin said Japan had no right to purchase the islands.
"The Chinese government will continue to take necessary measures to resolutely safeguard the sovereign rights of the Diaoyu Islands and adjacent islets," he said according to the Xinhua state news agency.
"The Diaoyu Islands and their adjacent islets have been inherent parts of Chinese territory since ancient times, and China has indisputable historical and jurisprudential evidence for this."
Noda's comments came after a report in the Asahi Shimbun said the government on Friday informed Tokyo's governor Shintaro Ishihara of its plan to buy three of the islands from their private Japanese owner.
In April, Ishihara announced he was in talks to buy the three islands -- Uotsurijima, Kitakojima and Minamikojima -- claiming that Japan was not doing enough to protect the territory.
The chain includes two other islands and an outcropping of rocks.
The influential daily said senior government officials were already negotiating with the owners, the Kurihara family, hoping to finalise the nationalisation plan by the end of the year.
The Tokyo metropolitan government said it had already collected more than 1.3 billion yen ($16.3 million) in donations from across the country to fund the purchase.
The governor confirmed later Saturday that senior government officials had visited him on Friday to apprise him about Noda's plan to put the three islands under state control.
"It could be a mere publicity stunt," said the outspoken Ishihara, well known for his nationalistic views. "If they really want to buy them, they should have said earlier."
The island chain, which lies in rich fishing grounds and may harbour valuable mineral reserves, was bought by the Kurihara family decades ago from descendants of the previous Japanese owners.
The islands were inhabited by Japanese fishermen before the end of World War II.
The waters around them have been the scene of territorial spats including the arrest of a Chinese trawlerman in late 2010 when he rammed his boat into two Japanese patrol boats.
On Thursday, two Japanese nationals swam to Kitakojima and stayed there for 90 minutes, the coastguard said.
Earlier this week Taiwanese vessels brushed against Japanese patrol ships in waters near the islands.