Danish inventor Peter Madsen has lost his appeal against the life sentence imposed for killing Swedish journalist Kim Wall on his submarine.

He was found guilty of premeditated murder and sexual assault in April, having previously admitted dismembering Ms Wall’s body.

However, Madsen, 47, argued a life sentence was “disproportionate”.

But appeals courts judges sided with the earlier decision, saying the case was one of “unusual brutality”.

The judges sitting at the Eastern High Court also said there were “aggravating circumstances” because the crime was “meticulously planned”.

• What really happened?
• Who is DIY submariner Peter Madsen?
• Kim Wall: ‘Exceptional journalist’ remembered

Ms Wall, 30, was last seen boarding Madsen’s homemade vessel in Copenhagen harbour in August 2017. Her dismembered body was found along the coast 11 days later.

Madsen claimed Ms Wall’s death was accidental during his trial at Copenhagen City Court, but prosecutors said he planned to kill her, either by suffocation or cutting her throat.

He announced his intention to appeal after judges handed him a life sentence, which equates to an average of 16 years behind bars in Denmark.

Madsen instead wanted a lighter, time-limited sentence.

His lawyer said they would look carefully at the ruling before deciding whether to take the case to the Supreme Court.

What do we know about the murder?

Ms Wall had been researching a story about Madsen’s venture and was last seen on the evening of 10 August as she departed with him on his self-built 40-tonne submarine, UC3 Nautilus, into waters off Copenhagen.

Her boyfriend raised the alarm the next day when she did not return from the trip. Madsen was rescued at sea after his submarine sank the same day. Police believe he deliberately scuttled the vessel.

Ms Wall’s mutilated torso was spotted by a passing cyclist on 21 August but her head, legs and clothing, placed in weighted-down bags, were not discovered by police divers until 6 October.

After his arrest, Madsen gave differing accounts of what had happened on board his submarine.

During the opening session of his trial, prosecutors said there was a suspicion that he had “psychopathic tendencies” after investigators discovered films on his computer showing women being tortured and mutilated.