COPENHAGEN (Reuters) - (This October 3 story has been refiled to Corrects detention period to four weeks, not four months, in seventh paragraph.)

Slideshow ( 2 images )

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

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 Wall was stabbed in her ribcage and genitals “around or shortly after her death,” was adding to the case against Madsen, the prosecutor, Jakob Buch-Jepsen, told the Copenhagen court.

DNA tests from Madsen’s nails, face and neck showed a clear match with Wall’s, Buch-Jepsen said, though the exact cause of death remained unknown. “Our suspicion hasn’t changed, it has been strengthened since (the last hearing on) September 5,” he added.

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

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.

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

Wall, a 30-year-old freelance journalist who was researching a story on Madsen, went missing after he took her out to sea in the 17-metre (56-foot) craft in August.

Madsen has told the court in past hearings 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 Wall’s.

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