Tokyo, Dec 12 (IANS/EFE): A Japanese woman, known as the "Black Widow of Kyoto" and suspected of killing seven of her partners, has admitted to poisoning her last husband with cyanide, investigative sources told Kyodo news agency Friday.

Chisako Kakehi, 68, was charged Thursday with the murder of her late spouse, Isao Kakehi, 75.

Authorities believe that the woman administered a lethal dose of cyanide (remains of which were found in her house) that caused his death in 2013 in the home they shared in Kyoto.

Chisako, dubbed by the media as the "Black Widow of Kyoto", denied the allegations when she was arrested Nov 19, although the sources quoted by Kyodo pointed out that days before she was formally charged, she finally admitted her involvement to the authorities.

Police took an interest in Chisako after it was discovered that she had inherited about $8.40 million paid by insurance companies and also assets inherited from her partners over the last 20 years.

Her arrest came after the autopsy of her fourth husband detected the presence of cyanide in his body.

Her first husband with whom she maintained a long marriage, died at age 54 in 1994 while the second died of a heart attack in 2006 at the age of 69 and the third died in 2008 at 75.

The woman then had three boyfriends, one died in 2009, and the other two in 2012 and 2013.

Cyanide blood compounds were also detected in the body of the husband who died suddenly in 2012 while driving his motorcycle.