Chisako Kakehi
Chisako Kakehi, who was arrested in KyotoJIJI PRESS/AFP/Getty Images

Japanese prosecutors have charged an elderly millionaire with murder after she was accused of poisoning her fourth husband.

Chisako Kakehi, 68, was dubbed the "black widow" by local media, after toxic cyanide was found in the body of her last husband, Isao Kakehi, 75. It later emerged that another six of her partners had died in mysterious circumstances.

Kakehi was arrested last month and denies the charges pressed against her by prosecutors in Kyoto.

Detectives said they discovered traces of cyanide in a sachet buried in dirt in a plant pot she discarded after her husband died, Kyodo news agency reported.

The man suddenly fell ill and died two months after their marriage in December last year.

"We suspect she did it for money," a detective with Kyoto police told AFP.

The news agency said that the woman has piled up a fortune of about 800m yen (£4.3m) in assets she received as inheritance from former partners over the last 20 years.

Police were investigating the death of at least one other of Kakehi's other six former partners, who also had traces of poison in his blood.

"We can't say how many now... Given their advanced age, we have to proceed carefully to judge whether their deaths were actually the result of foul play or not," the detective said.

A few months before her last husband passed away, another 75-year-old she was dating died of a sudden disease, after the couple dined at a restaurant, Jiji Press reported.

Another two boyfriends died; one in 2009 of cancer, and another in 2012 after a driving accident.

The latter collapsed while riding his motorbike and traces of cyanide were later found in his blood, local media reported.

Kakehi's first husband died aged 54 in 1994, the second followed in 2006 while the third met his demise two years later.

Kakehi has protested her innocence, telling Jiji Press in an earlier interview she is "doomed by fate".