COPENHAGEN — The Danish inventor Peter Madsen was formally indicted on Tuesday on charges of homicide in connection with the death in August of Kim Wall, a Swedish journalist who had boarded his submarine to interview him.

Danish prosecutors and the Copenhagen police indicted Mr. Madsen on charges of killing Ms. Wall “with prior planning and preparation” — the equivalent of murder — according to a statement released by the police, as well as with dismemberment, indecent handling of a corpse and improper sexual relations. While a news release was posted online on Tuesday, the actual wording of the charges is expected to be made public only next week.

Ms. Wall, a freelance journalist, vanished on Aug. 10 after leaving the port of Copenhagen on the UC3 Nautilus, a submarine that Mr. Madsen had built and operated. Her torso was found on a beach on Amager Island near Copenhagen after 11 days, and divers later recovered her severed head and legs in plastic bags.

Mr. Madsen, 47, has given various explanations for the disappearance of Ms. Wall, 30. But he eventually said that she had died onboard his vessel after a hatch unexpectedly collapsed, and that she had hit her head while she was climbing stairs in the submarine’s tower. An autopsy revealed that she had no head injuries to support that claim, however.