Madsen told the court on Tuesday that a 70kg hatch door fell on her head by accident, killing her instantly and causing her to bleed from the head. In a panic, he threw her overboard, he said, insisting the body was intact.

“I lose my foothold and the hatch shuts,” he said. “Kim had been severely hurt and was laying with an intense bleeding. There was a pool of blood where she had landed.”

“In the shock I was in, it was the right thing to do,” Madsen told the court, adding that he had even contemplated taking his own life.

The 46-year-old has been held in custody since August 12 suspected of “negligent manslaughter”.

But Danish prosecutors asked the court to extend Madsen’s detention, alleging that he murdered Wall and desecrated her body.

Prosecutor Jakob Buch-Jepsen accused Madsen of “having killed Kim Wall in an undetermined fashion, then he dismembered the body, he cut the torso and tied a pipe to it with the intention of sinking it to the seabed”.

Madsen admitted on Tuesday to desecrating the body by tossing it overboard but denied having mutilated it.

Madsen’s version of events came to light after the judge rejected the prosecution’s request that the hearing be held behind closed doors.

The prosecution had argued that an open hearing would jeopardise the investigation. It also called for Madsen to undergo a psychiatric evaluation.

Authorities are still searching for the rest of Wall’s remains, which they hope will provide some clues about the cause of death.

Investigators have not commented on what alleged motive Madsen would have had for killing Wall.

Madsen insisted that there was no sexual relationship between him and Wall, saying their contact had been purely professional.

After Wall failed to return home following her interview on August 10, her boyfriend reported her missing on August 11. That same day, Madsen was rescued from waters between Denmark and Sweden shortly before his submarine sank.

Investigators recovered and searched the vessel, which police believe Madsen sank intentionally.

After scanning the sub to rule out any hidden compartments and to “search for clues to the crime”, the police announced nothing new had been found.

Madsen is an eccentric self-taught engineer. In addition to launching his home-made submarine, he has also successfully launched rockets with the aim of developing private space travel.

The Nautilus was the biggest private sub ever made when Madsen built it in 2008 with help from a group of volunteers.

The volunteers were engaged in a long-running dispute over the Nautilus before members of the board decided to transfer the vessel’s ownership to Madsen, according to the sub’s website.

“That curse is me. There will never be peace on Nautilus as long as I exist,” Madsen wrote, according to the volunteers.

Madsen has drawn media interest for his ambitions to pursue amateur space travel?

“My passion is finding ways to travel to worlds beyond the well-known,” he wrote on the website of his Rocket Madsen Space Lab.

Danish police are still searching for the clothes Wall wore on the submarine: an orange fleece, a skirt and white sneakers.

Wall worked as an editorial intern and reporter in Hong Kong for the South China Morning Post from June to September, 2013, covering news about China for the national desk.

In addition to The South China Morning Post, her work has appeared in Harpers, The Guardian, The New York Times, Foreign Policy, The Atlantic and many other publications.