Peter Madsen, the Danish inventor, has confessed to sawing off the head and limbs of Swedish journalist Kim Wall and also changed his story about how she died on board his submarine, Copenhagen police said on Monday.

Mr Madsen, 46, now maintains that Wall died from carbon monoxide released into the deck of the submarine while he steered unawares from the conning tower, investigators said in a statement.

He continues to deny murdering her.

"He's claiming that there wasn't enough oxygen in the submarine and that she suffocated, and that he was upstairs and didn't notice and found her when he came back," said Steen Hansen, a press officer at Copenhagen police.

Madsen gave his changed account on October 14 at an interview arranged by his defence lawyer Betina Hald Engmar, after police presented DNA evidence found on his clothes.

"We worked hard to find evidence on his clothes that he had dismembered the body, and now we have found the evidence, he has changed his story," Hansen said.

"Now we have to talk to people who know the submarine to see if it's a possibility."

On September 5, Mr Madsen told a court that the 30-year-old had been killed when a metal hatch crashed onto her head, fracturing her skull.