COPENHAGEN, Denmark (AP) — Inventor Peter Madsen was charged Tuesday with killing Swedish journalist Kim Wall during a trip on his private submarine, with prosecutors saying he either cut her throat or strangled her.

Prosecutor Jakob Buch-Jepsen said the case is "very unusual and extremely disturbing."

Madsen is charged with murder as well as indecent handling of a corpse for the way he disposed of Wall's body.

Madsen claimed Wall died accidentally inside the submarine while he was on deck during the excursion in August. However, he later admitted throwing her body parts into the sea.

Madsen and Wall had gone on a trip in Madsen's submarine on Aug. 10. Wall, who was working on a story about Madsen, was last seen aboard the vessel as it left Copenhagen. The next day, Madsen — an entrepreneur who once dreamed of launching a manned space mission — was rescued from the sinking submarine without Wall.

Police believe he deliberately sank the vessel.

Madsen has offered a shifting variety of explanations for Wall's death. Initially, he told authorities he had dropped Wall off on an island several hours after their voyage began. Later, he said she had died in an accident on board and he had "buried" her at sea.

Her dismembered, naked torso was found on a southern Copenhagen coast in late August and her head, legs and clothes were discovered in bags at sea in October. Heavy metal objects were designed to take them to the ocean floor.

The trial starts March 8 and a verdict is expected on April 25.