TAIPEI (AFP) - A Taiwan court on Thursday upheld a death sentence on a "merciless" woman who murdered three close family members in an insurance scam.

The final ruling in the high-profile case made Lin Yu Ru the first woman to be sentenced to death in Taiwan for 23 years.

The 32-year-old, accused of murdering her mother, husband and mother-in-law for $NT20 million (S$828,000) in insurance money, was convicted and sentenced to death by a High Court last year.

Her appeal was rejected by the Supreme Court on Thursday after a hearing last month.

"What she did was cruel and merciless... the pain she caused to her husband's family was unendurable," the court said in a statement.

In an interview with local television, a relative of the victims hailed the ruling and described it as a "belated justice".

The court statement said Lin admitted to pushing her mother down the stairs and poisoning her husband and mother-in-law to get the insurance money and pay off gambling debts.

She came under suspicion because the three died mysteriously within nine months of each other and she was the sole beneficiary of the insurance money.