Peter Madsen, 46, previously claimed they both escaped the submarine, which sank, alive, but now says she died onboard so he "buried her at sea", according to Danish police.

Mr Masden, who has been accused of negligent manslaughter, "told police and the court that there was an accident on board the sub that led to the death of Kim Wall, and that he subsequently buried her at sea in an undefined location of the Koge Bay" south of Copenhagen, police said in a statement.

The court case is taking place behind closed doors but the police revealed the inventor's explanation after a request from the defence and prosecution.

Danish authorities have been searching for Wall, a 30-year-old reporter who had been writing a feature story about Madsen, since she failed to return from an interview with him aboard the 60-foot (18-metre) Nautilus.