Chisako Kakehi in a file photo taken in March 2014

A convicted serial killer in Japan, dubbed the Black Widow, has lost her final appeal to avoid execution.

Chisako Kakehi, 74, killed three of her partners, including her husband, and attempted to murder a fourth man.

Kakehi pocketed millions in inheritance and insurance payouts after poisoning her victims with cyanide.

Her lawyers appealed the 2017 sentence, arguing that she suffers from dementia and does not understand the legal proceedings.

But Japan’s Supreme Court rejected the appeal, clearing the way for her death sentence to be finalised.

Kakehi became known in Japanese media as the Black Widow, after the female spider which kills its mates after sex.

The trial in 2017, which lasted more than four months, heard that she had joined matchmaking services and specifically requested to meet men who were rich and childless.

She was found guilty of killing two boyfriends and her husband, all aged between 70 and 80, between 2007 and 2013.

Her husband, 75-year-old Isao Kakehi, died a month after they got married in 2013.

Kakehi reportedly received around one billion yen ($8.8m; £6.5m) after the deaths, although she lost much of it in the stock market and fell into debt, Japan Times reports.

She was also convicted of the attempted murder and robbery of another man, who has since died of cancer.

Kakehi had three other husbands who also all died, but she has not been charged in connection with their deaths.