Here is a brief outline of the governments' competing claims to what Japan calls Senkaku and China calls Diaoyu.

JAPAN

Tokyo says its government began surveying the islands in 1885 and found them unoccupied with "no trace of having been under the control of China".

Ten years later, on January 14 1895, the cabinet decided to erect a marker to formally incorporate the Senkaku Islands into Japanese territory, the foreign ministry says.

"Since then the Senkaku Islands have continuously remained as an integral part of the Nansei Shoto Islands which are the territory of Japan," it says.

Tokyo says the isles were not included in territory Japan renounced under the San Francisco Peace Treaty, which officially ended World War II, and that Beijing expressed no objection at the time to their exclusion.

China and Taiwan began claiming the islands after 1970, after the possibility emerged of energy reserves being found in the seabed nearby, Japan says.

It added that the islands that were nationalised on September 11 were previously owned by the Government of Japan until 1932 when a private citizen acquired them.

Japan says this month saw no more than "a nominal transfer of real property under domestic law, which is not a major change of the current situation".

As such, this purchase "should not raise any issues with other countries or region.

"There is no change in the policy to ensure a continued peaceful and stable maintenance and management of the islands over the long term."

CHINA

China's claims date back to the Ming Dynasty (1368-1644) when reference to the Diaoyu Islands appeared on maps and in a book during the reign of Yong Le (1403-1424), according to the Chinese government.

China also insists that a map published by Japan in the 1780s underlines the Chinese claim to islands.

Beijing says the dispute over the islands' sovereignty only emerged when they were ceded to Japan -- along with Taiwan -- at the end of the 1894-5 Sino-Japanese war, which China calls an "illegal" Japanese occupation.

After World War II, Tokyo relinquished its claim over Taiwan and the Penghu islands, which are located in the Taiwan Strait.

China says the Diaoyu islands were also supposed to have been returned to China but have wrongly remained in Japan's hands.

Taiwan separately claims ownership of the islands.

Wang Xuemei, a forensics official with China's national prosecutor's office, told AFP a court's conclusion that the wife of one of China's top politicians poisoned businessman Neil Heywood with cyanide was flawed.

"That our court went so far as to believe the conclusion that cyanide was the cause of death is very distressing, unsettling and scary," Wang said.

Wang noted that she had no direct involvement in the case and did not examine evidence first-hand, but her doubts echo those of many Chinese that the case was being manipulated to minimise embarrassment to the ruling Communist Party.

Gu Kailai, the wife of rising political star Bo Xilai -- former top Communist official in the southwestern municipality of Chongqing -- was sentenced in August to a suspended death sentence that will likely be commuted to life in prison.

The emergence of the case earlier this year triggered the political downfall of her husband, who was seen as a potential candidate for elevation to the top echelons of party power at a Communist Party meeting expected to be held within weeks.

No legal action has yet been taken against Bo.

Wang, who also is deputy director of the Chinese Forensic Medicine Association, said court documents and testimony describing the sequence of events in Heywood's death do not fit with what happens in a cyanide poisoning.

Cyanide poisoning causes immediate asphyxia, spasms and a heart attack and turns the skin and blood bright red, she said, adding that reports on Heywood's death that she has seen do not indicate such symptoms.

"I have serious suspicions over the blood samples that Wang Lijun controlled for three months and then suddenly produced as the fatal poison," she said.

Bo's right hand man, Wang Lijun, who was formerly vice mayor and police chief of Chongqing, was sentenced this week to 15 years in prison for attempting to cover up the murder, as well as other crimes.

The scandal emerged in February when Wang fled to the United States consulate in Chengdu city, apparently fearing for his life after he revealed to Bo that his wife was involved in the murder.

Wang Xuemei, who first aired her doubts in a blog posting that has since been removed by China's censors, refused to speculate on why or how the court reached its conclusion on cyanide.