A nanny who murdered and chopped up her employers after their two-month-old baby accidentally died in her care has been jailed for 20 years.

Chinese national Hui Zhang, 34, used an electric saw to dismember Ying Wang and Liangsi Xui's in the bathroom of her Paris home after turning on the washing machine to cover the noise.

A French court heard she killed the grieving couple after a meeting at her home turned violent following their son's death, reports the French newspaper Liberation.

Hui, who admitted the double murder, claimed she acted in self-defence after the parents attacked her boyfriend, Te Lu, also 34, with a butcher's knife.

At the trial's opening, Hui said: “It’s true, I killed them, and I will regret it for the rest of my life,” reports the AFP for The Local.

Hui and Te had invited the parents to their home and offered them money to try to get them not to report the death of their baby. But the encounter did not unfold as planned and Hui killed the couple with a small axe, writes French newspaper Le Figaro.

Te told the court he fell unconscious during the fight and remained so while Hui chopped up the two bodies in the bathroom.

“I was sucked into a whirlwind of nightmares but I am innocent,” Te told the court.

Te admitted helping Hui to get rid of the remains, which she had wrapped into rubbish bags, and they hid them in the forest of Vincennes, east of Paris, and in bins.

In June 2012, the case was unveiled when two joggers found a leg, cut off at the ankle, in the Vincennes forest. Several days later, a guide dog dug out a human torso, but searches to find the remaining body parts were fruitless.

Before the bodies were identified, Hui and Te turned themselves in to the police station and indicated where they had hidden the other body parts to police officers.

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The baby's body was never recovered.

The judge followed the prosecutor’s recommendation of 20 years behind bars for Hui, but her boyfriend and co-defendant was acquitted.