German police have arrested five members of a South Korean family suspected of beating to death a 41-year-old woman in a religious exorcism ritual in a hotel room.

The relatives allegedly believed that the woman, also South Korean, was “possessed by demons” and tied her to a bed, gagged and severely beat her for two hours with the goal of “driving out the devil”, prosecutors said.

“I have never seen anything like it,” said Nadja Niesen, chief prosecutor of the city of Frankfurt.

The body was found Saturday in a hotel room where the five suspects – a 44-year-old woman, her 21-year-old son and 19-year-old daughter, and two boys aged 15, one of whom was the victim’s son – were arrested on suspicion of murder.

The cause of death was “suffocation due to massive chest compression and trauma to the neck”. Officials said the woman’s killers used “severe violence” against her, beating her chest and stomach while gagging her with a towel and then a cloth-covered coat hanger.

The national news agency DPA reported that the family were of unknown religious affiliation and had arrived in the city around six weeks earlier.

The investigation led police to discover a second suspected victim alive in the garage of a house the group had rented in the town of Sulzbach. The female relative was badly injured, had hypothermia and was dehydrated.