A former millionairess known as Japan's "Black Widow" has been sentenced to death by hanging.

Chisako Kakehi, 70, made her elderly lovers drink cyanide before claiming millions of euro from their life insurance policies and inheritance.

She was sentenced to death for the murder of three men, one of them her husband, and the attempted murder of another.

Judge Ayako Nakagawa told Kyoto District Court that she had showed a "murderous intention in all the four cases", according to broadcaster NHK.

Prosecutors said Kakehi had met some of the men - most of them elderly or ill - through dating agencies.

She had reportedly stipulated that any potential partners should be wealthy and childless.

Once she had been made beneficiary of her victims' life assurance policies, she killed them, the court heard.

She made one billion yen (€7.6m) before losing most of it through failed financial trading.

Cyanide was found in the bodies of at least two of the men and traces were found in the rubbish at Kakehi's home in Kyoto.

At her apartment there was also paraphernalia for administering the drugs.

Kakehi's lawyers had argued she is not criminally responsible for the murders because she suffers from dementia, but the judge had rejected this.

When the trial began in June she had seemed determined to remain silent.

But she later admitted to killing her fourth husband in 2013 "because he gave other women tens of millions of yen but did not give me even a penny", according to Jiji Press.

She reportedly told the court: "Even if I were executed tomorrow, I would die smiling."

Her lawyers are understood to be preparing to appeal against her conviction.