A FORMER Winchester schoolboy was using cocaine when he killed two Indonesian women by slitting their throats and then used his phone to film himself talking about it, a court in Hong Kong has heard.

Banker Rurik Jutting entered a plea of not guilty to two murder charges that were read out at the High Court, with prosecutors rejecting his attempt to plead guilty to the lesser charge of manslaughter over the 2014 killings.

Jutting, who attended Winchester College, is charged with the murders of Sumarti Ningsih, 23 and Seneng Mujiasih, 26, whose bodies were found in his luxury apartment near the Asian financial centre's Wan Chai red-light district, in a case highlighting the Asian financial hub's inequality and privileged lifestyle of its wealthy expat elite.

Jutting is a Cambridge University graduate who worked for Bank of America-Merrill Lynch in structured equity finance and trading. If convicted, he faces life in prison.

The case shocked the former British colony, which has a reputation for being safe, while also highlighting the city's extreme inequality.

The case is "particularly horrifying" because it includes photographic evidence of one victim's torture, the judge told prospective jurors as the trial got under way.

In opening remarks, Prosecutor John Reading told jurors that, according to the facts agreed on by both sides, Ms Sumarti went home with Jutting after he offered her "a large sum of money" on October 25 2014.

Ms Sumarti, who was in Hong Kong on a tourist visa, had a five-year-old son living with her parents in Indonesia, he said.

Jutting subjected her to "increasingly cruel acts of violence using his belt, sex toys, a pair of pliers and his fists", Mr Reading said.

He said the pair had previously met when he paid to have sex with her. But on that occasion, because he had been so rough, she offered to give back half the money if she could leave early, which he agreed to.

Jutting used his phone to film himself talking about the killing, how he enjoyed dominating Ms Sumarti and how he watched pornographic videos involving extreme violence.

He also said he "definitely could not have done that without cocaine".

In some shots, Ms Sumarti's body can be seen on the floor of the shower. At one point he wrapped it up and put it in a suitcase that he left on the balcony.

Late on October 31 2014, Jutting took Ms Seneng back to his apartment. She was officially in Hong Kong as a foreign maid but was working at a bar when Jutting offered her money for sex, Mr Reading said.

After they undressed, Ms Seneng spotted a gag made of some rope that he had left next to the sofa and started to shout, Mr Reading said.

Jutting grabbed her, took a knife he had hidden under a cushion, held it to her throat and told her he would cut her throat if she didn't stop.

"She continued to struggle and shout, and he cut her throat," he told the jurors.

He made more video recordings, including one that showed Ms Seneng's body, and told police he used up the rest of his cocaine. He apparently started hallucinating and, believing that the police were coming to get him, called the emergency number.

Officers who arrived found the body and arrested him. In interviews, he told police everything that happened as well as discussing his drug use.

Mr Reading said traces of cocaine were detected in more than two dozen small plastic bags found in Jutting's apartment.

Jutting, who watched from the glass-screened dock, wore a dark blue shirt, dark-framed glasses and looked much slimmer than in court appearances last year.

When the clerk asked what his plea was to the two murder charge, he replied "Not guilty to murder by reason of diminished responsibility but guilty of manslaughter", which the prosecutors refused to accept, meaning the trial on the murder charges will proceed.

A third charge was also read out - unlawful burial of Ms Sumarti's body - to which he pleaded guilty.

Judge Michael Stuart-Moore told jurors before the selection began that the evidence includes "extremely upsetting" colour photos.

"Much of what the jury will see or hear is very disturbing indeed," he said, but added that the Jutting is entitled to a fair trial.

While Jutting's initial guilty to manslaughter plea was rejected, the judge told jurors that they could still decide between finding him guilty of murder or manslaughter.

There are more than 300,000 migrant domestic workers employed in Hong Kong, almost all of them women from Indonesia or the Philippines.