PARIS (AFP) - A Chinese nanny admitted in a Paris court on Tuesday (Jan 19) to killing and dismembering the parents of a baby who had died in her care, in a gruesome case worthy of a horror movie.

"It's true, I killed them, and I will regret it for the rest of my life," the diminutive Hui Zhang, 34, said at the start of the hearing.

Hui said she merely acted in self-defence as the furious parents of the dead newborn attacked her and her boyfriend with a butcher's knife.

Her boyfriend and co-accused Te Lu, also 34, denied helping Hui kill the couple.

"I was sucked into a whirlwind of nightmares but I am innocent," he told the court.

The case first came to light in June 2012 after two joggers came upon a leg, cut off at the ankle, in the Vincennes forest on the edge of the French capital.

Several days later, a guide dog found a human torso in the same area, but the hunt for further remains was fruitless.

The police knew the victims were Asian and initially thought the murders could be the work of the Chinese mafia, or of Luka Rocco Magnotta, a Canadian convicted of killing and dismembering a Chinese student who spent time in Paris.

But before the bodies could even be identified, Hui and Te turned themselves in.

Hui told the police she had been babysitting a two-month-old baby who died in his sleep.

She and her partner decided to offer the child's parents money to try to get them not to report the boy's death.

They invited the parents to their home, but said their plans quickly went awry faced with the fury of the grieving couple.

"My client maintains she was acting in self-defence," said the nanny's lawyer Alexis Guedj.

A lawyer for the family of the child's mother, Ms Chloe Arnoux, argued that the defendants prepared for the meeting by equipping themselves with sharp weapons.

She said Hui "was not able to tell them to their faces that their child was dead, so she brought the baby's body into the sitting room".

Hui then chopped up the two bodies in the bathroom with an electric saw, using the washing machine to cover the noise.

She then wrapped the body parts in rubbish bags and scrubbed her apartment clean.

A reconstitution of the crime scene showed that Hui, despite her small size, could drag the two bodies and lift them into the bathtub.

Te confirmed her version of events. He said he fell unconscious during the fight and remained so while Hui cut up the bodies.

"He was violently hit, it has been medically recorded," said Te's lawyer Eric Dupond-Moretti, arguing that his client was not complicit in the murder.

When he came to he helped her get rid of the remains, transporting them "by foot or public transport", said a policeman.

After the couple turned themselves in, they directed the police to the locations of more body parts around the forest.

However they did not find the baby's body, which Hui said she had thrown in rubbish bins along with some of the other remains.

The police say there were no indications that Hui and Te, who arrived in France in 2004, were predisposed to this sort of grisly crime.

Hui has been described by investigators as a highly intelligent and forceful character. Witnesses say she was the dominant partner in her relationship with Te, who was a business adviser.

After the murders, they went to China and closed their bank accounts in France, but returned soon after.

They say they had always intended to return, but the police claim they were worried about facing the death penalty in China.

The trial will continue until Friday.