COPENHAGEN, Denmark -- A Danish prosecutor says inventor Peter Madsen has been charged with murdering Swedish journalist Kim Wall during a trip on his private submarine, saying he either cut her throat or strangled her.

Prosecutor Jakob Buch-Jepsen said Tuesday the case is "very unusual and extremely disturbing."

Madsen, 47, is charged with murder, dismemberment and indecent handling of a corpse for the way he disposed of Wall's body. He is also charged with having sexual relations with Wall, 30, of a "particularly dangerous nature" before she was killed.

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The charges were made public by the Danish prosecution authority.

Buch-Jepsen said the killing was premeditated. Prosecutors will urge that Madsen be sentenced to life in prison, or be locked up in a secure mental facility if deemed necessary by psychiatrists for as long as he's considered sick and dangerous to others.

Peter Madsen, Danish inventor, engineer, rocket- and u-boat builder, talks about entrepreneurship during Danish Business Day event held in Copenhagen, Denmark, May 9, 2017. REUTERS

"There is much technical evidence but I won't go into details right now," Buch-Jepsen told a brief news conference. He also declined to comment on Madsen's motive.

"Evidence must be presented in court and not in the media," he said, adding he also didn't want to comment out of respect for Wall's family.

Madsen's defense lawyer Betina Hald Engmark had no immediate comment in reaction to the charges, adding her client still denies murdering Wall.

Madsen claims Wall died accidentally inside the submarine while he was on deck during the excursion in August. However, he has admitted throwing her body parts into the sea.

The start of the trial has been set for March 8. A verdict is expected April 25.

The Submarine UC3 Nautilus is lifted onto a block truck from the salvage ship Vina with the help of a container crane in Copenhagen's Harbor, on August 12, 2017. Getty

In November, divers found a right arm in the sea south of the Danish capital that is believed to have been Wall's. Police investigator Jens Moeller Jensen said it was found over half a mile from where Wall's decapitated head and legs were discovered in plastic bags the previous month.

He said it was held down in the same way as a left arm found nearby, involving plastic strips and pieces of pipes.