Danish submarine owner and inventor Peter Madsen lands with the help of the Danish defence in Dragor Harbor south of Copenhagen, Denmark August 11, 2017. — Scanpix Denmark/Bax Lindhardt/via Reuters

STOCKHOLM, Aug 21 — The Danish inventor of a do-it-yourself submarine has said that a Swedish journalist missing since August 11 died in an accident onboard the vessel, and that he dumped her body in the sea, Danish police said today.

The inventor, Peter Madsen, had been claiming that he last saw Kim Wall when he dropped her off on the tip of an island in Copenhagen late on August 10.

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 18-metre (60-foot) Nautilus.

But Madsen, 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 two were sighted onboard the vessel by several people in waters off Copenhagen the evening of August 10.

The sub was also reported missing, but rescue crews located it around midday on August 11 in Koge Bay, about 50 kilometres (30 miles) south of the Danish capital.

Just after being found, Madsen was rescued and the submarine suddenly sank.

The Nautilus was the biggest private sub ever made when Madsen built it in 2008. — AFP