Video footage that appears to show one of late Libyan dictator Moammar Gaddafi's sons being tortured has sparked condemnation from human rights groups, with Libya's state prosecutor pledging to investigate, according to the news agency Reuters.

The nine-minute video, released Sunday on the Clear News Web site, shows 42-year-old Saadi Gaddafi being interrogated and slapped around the face in al-Hadba prison in Tripoli.

Towards the end of the video, Gaddafi is asked whether he would prefer to be beaten on his feet or his buttocks. "What kind of question is this?" he responds. "My feet." Gaddafi is then placed on his back with his feet elevated and beaten with a pipe, causing him to scream in agony.

For much of the video, it appears that a number of other men are being beaten just outside the room; at one point, Gaddafi is made to watch. There is no indication that Gaddafi or any of the other prisoners have any legal representation.

Melinda Taylor, a lawyer at the International Criminal Court who represents Gaddafi, told RT that it did appear to be her client in the video and that "being in al-Hadba subjects him both to the maximum sentence and to the maximum mistreatment" because of his family name.

“The graphic video that seems to show prisoners being beaten raises serious concerns about the methods used to interrogate al-Saadi Gaddafi and other detainees at al-Hadba prison,” said Joe Stork, deputy Middle East director at Human Rights Watch. "The Tripoli authorities need to urgently establish exactly what did occur, put in place measures to protect all detainees from abuse, and hold anyone responsible for that kind of treatment to account.”

It is unclear when the footage was filmed or how it came to be made public. However, the release of the video comes less than a week after Saif al-Islam Gaddafi, Saadi's brother, was sentenced to death by a court in Tripoli, along with eight former allies of his father. Saif is being held by a militia in the mountain town of Zintan that opposes Libya Dawn, a coalition of militias that controls Tripoli. It is unclear whether he will be handed over.

While his older brother was considered the heir apparent to Moammar Gaddafi, Saadi Gaddafi was better known for his love of football, including a brief and uneventful career at a number of Italian clubs, and reports of a playboy lifestyle. He fled Libya in 2011 but was held under house arrest in Niger and extradited in March 2014. Shortly after his return to Libya, Tripoli authorities released a video showing him apologizing to the Libyan people and denying rumors that he had been tortured.

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