A Danish inventor charged with murdering Swedish journalist Kim Wall in his homemade submarine had video footage on his computer showing women being violently killed, a court heard on Tuesday.

Key points: Peter Madsen charged with murdering reporter Kim Wall on his submarine

Peter Madsen charged with murdering reporter Kim Wall on his submarine Madsen claims Ms Wall died accidentally

Madsen claims Ms Wall died accidentally Court reveals disturbing videos were found on Madsen's computer

A police prosecutor said officers found images "which we presume to be real" of women being strangled and decapitated on the hard drive on Peter Madsen's computer in a laboratory he ran.

That, together with new post-mortem evidence showing Ms Wall was stabbed in her ribcage and genitals "around or shortly after her death", was adding to the case against Mr Madsen, prosecutor Jakob Buch-Jepsen told the Copenhagen court.

Mr Buch-Jepsen said DNA tests from Madsen's nails, face and neck showed a clear match with Ms Wall's, but the exact cause of death remained unknown.

"Our suspicion hasn't changed, it has been strengthened since [the last hearing on] September 5," he said.

Mr Madsen, who denies murdering Ms Wall and another charge of mutilating her body, appeared in court via video link dressed in a green boilersuit.

Swedish journalist Kim Wall went missing while researching the Danish inventor. ( AP: Tom Wall, file )

He said the computer searched by police was not his.

"They are the space laboratory's tools which have been used by everyone in the laboratory," he said.

The court heard he had been working on building a space rocket in the lab.

Journalist went missing at sea

Mr Madsen remained calm during the pre-trial session, sitting with his hands folded most of the time. The court ordered him to be detained for another four months as investigations continued.

Ms Wall, a 30-year-old freelance journalist who was researching a story on Mr Madsen, went missing after he took her out to sea in the 17-metre submarine in August.

Kim Wall was on Peter Madsen's UC3 Nautilus before the sinking ( Wikipedia Commons: Frumperino )

Mr Madsen has told the court in past hearings Ms Wall died accidentally, saying she was hit by a heavy hatch cover on his UC3 Nautilus submarine.

On August 23, police identified a headless female torso washed ashore in Copenhagen as Ms Wall's.

Mr Madsen also denied amputating her limbs, saying he tried to bury her whole body at sea.

Reuters