Image copyright Getty Images Image caption Rurik Jutting previously worked at Bank of America in Hong Kong

A British banker accused of murdering two Indonesian women in Hong Kong has pleaded not guilty on grounds of diminished responsibility.

As his trial opened, Rurik Jutting pleaded guilty to a lesser charge of manslaughter but this was rejected.

Police found the bodies of Sumarti Ningsih and Seneng Mujiasih in Mr Jutting's apartment in November 2014.

The banker, 31, faces a possible life sentence if convicted in what is Hong Kong's biggest murder trial in years.

Jurors were warned that Mr Jutting had filmed both women on his phone and that they would have to see "extremely upsetting" images during the trial.

Read more: Sumarti Ningsih's story

Image copyright Unknown Image caption Sumarti Ningsih's body was found in a suitcase decomposing

Mr Jutting, who has been detained at a maximum security prison since his arrest, has already been deemed psychiatrically fit to stand trial.

He also pleaded at the High Court to a third charge of unlawful burial of a body.

Calm and collected defendant: Danny Vincent, BBC News, Hong Kong High Court

Rurik Jutting appeared noticeably thinner in court than during his earlier pre-trial hearings. He arrived flanked by four police officers.

Clean-shaven, he wore a smart blue shirt and black spectacles. The Cambridge-educated banker took notes and appeared calm and collected as he pleaded not guilty to murder on the grounds of diminished responsibility.

The jury were warned that they would be expected to look at extremely violent evidence during the trial.

The court heard that the defendant had recorded scenes of torture inflicted on his first victim on his phone.

Prosecutor John Reading said Sumarti Ningsih had been tortured for three days at Mr Jutting's luxury flat in Hong Kong's Wan Chai district.

He eventually killed her with a serrated knife in the shower, Mr Reading added, and hid her body in a suitcase.

The prosecution says that days later Mr Jutting met Seneng Mujiasih at a bar in Wan Chai and took her to his flat where he later cut her throat.

"In one of his interviews with the police, the accused explained how he went out that evening hunting for prey, and that Mujiasih was his prey," Mr Reading said.

Image copyright AP Image caption A group campaigning for migrant workers' rights staged a protest outside court as the trial began

Police were called to Mr Jutting's apartment on 1 November 2014.

They found the body of Seneng Mujiasih with knife wounds to her neck and buttock, police reports at the time said. Later they found the body of the other victim in a suitcase decomposing. Both women were in their 20s.

The gruesome deaths shocked the city, widely considered among the safest in the world.

The case is being closely watched by migrant workers in Hong Kong and a group campaigning for their rights staged a protest outside the court on Monday.

Mr Jutting worked at Bank of America-Merrill Lynch as a securities trader up until a few days before the discovery of the bodies.