A former South Korean university professor was sentenced to 12 years in prison on Thursday for habitually beating his former pupil and forcing him to eat human feces and drink urine.

Three other people were sentenced to three to six years in prison for participating in the abuse that went on for more than two years, said the Suwon District Court, which was confirming a ruling made at its branch court in Seongnam City.

Prosecutors had sought a prison term of 10 years for the 52-year-old former professor, but the judges hit him with heavier punishment because the cruelty of his actions was "beyond imagination," the court said.

Police said the former professor began abusing the victim, 29, one of his former students, after hiring him at a non-profit organization he ran in 2013. The three other defendants were also former students he employed at the organization.

The former professor and the other defendants habitually beat the victim with a baseball bat and other items over what they said were professional mistakes and poor character. The defendants would also cover the victim's head with a plastic bag and spray pepper spray inside it, and force him to eat their feces and drink their urine from plastic bottles. The abuse inflicted serious injuries to the victim, who underwent surgery last year to repair damages to his right thigh, the court said.

The victim told police he tolerated the abuse until earlier this year because he had hoped the former professor would help him get a job. The former professor was expelled from his university in August.