It is not clear when or how the video was filmed, but it was posted by an Arabic website and has been widely circulated on social media.
The undated video is also clearly edited.
In the video, Saadi Gadhafi is seen blindfolded at first sitting in an office in what is believed to be al-Hadba prison in Tripoli, where he has been held since his extradition from Niger last year
The blindfolded Gadhafi, in a green tracksuit with a shaved head, is made to listen to what sounds like the tormented screams of other prisoners being beaten up outside the room.
Several men in the video believed to be guards and prison officials -- some in uniforms, others in civilian clothing -- can be seen interrogating Gadhafi.
At one point, a seemingly distressed Gadhafi pleads to someone else in the room for a break.
"I swear to God, if you give me rest I will give you all the information," he says.
Insulted, slapped and hit with stick
Gadhafi's blindfold is later removed, and he is made to watch a man outside the room being hit with a stick.
Later, the video shows Gadhafi being insulted, slapped on the face and beaten with a stick on the soles of his feet.
"(The video) raises concerns about the interrogation methods that are being used at this particular prison in Libya," said Hanan Salah from the advocacy group Human Rights Watch.
"Not just concerns about Saadi Gadhafi -- who is currently in pre-trial detention, and we saw in that awful video being interrogated and probably coerced into answering certain questions -- but our concern goes for the other detainees who are in that particular prison, which include other former officials of the Gadhafi regime including Abdullah al-Senussi, AbuZeid Dorda and al-Baghdadi al-Mahmoudi."
Al-Senussi is Libya's former spy chief, while the other two men were once prime ministers.
The three were among nine other officials sentenced to death by firing squad last year by a Tripoli court in the same facility. An older Gadhafi brother, held by a militia in the city of Zintan since his capture in 2011, was also sentenced to death in absentia.
The sentences capped a more than one-year long trial that elicited an uproar by rights groups and the United Nations, which characterized it as flawed and unfair.
In a statement posted on its Facebook page, the office of Tripoli's Prosecutor General said it had launched an investigation into the incident after the video circulated online. The statement promises legal action against those involved in any violations.
Militias roam free in a lawless state
In the chaos that followed the 2011 revolution, Libya has become a lawless state in which militias operate freely and the country's judiciary has struggled to bring perpetrators of countless attacks and crimes to justice.
"We have seen many announcements from the general prosecutor about investigations that actually never take place. There have been other complaints and other complaints of ill treatment at this particular prison ... and we haven't seen the general prosecutor move or conduct any serious investigations," said Salah of Human Rights Watch.
Unlike his brother Saif al-Islam Gadhafi
, Saadi is not wanted by the International Criminal Court. He has yet to stand trial in Libya, where he is accused of murdering a Libyan football player during his time as head of the North African country's football federation.
The former businessman was known for his love for football; he even had a short-lived career as a professional player in Italy.
As the Gadhafi regime crumbled in 2011, Saadi fled to neighboring Niger, where he stayed until Libya managed to secure his extradition in March of last year
Allegations of abuse and torture emerged shortly after his arrival in Libya, prompting officials to release several videos on state TV, including one where he says he is being treated well.
In another video, Gadhafi addresses the Libyan people and apologizes
for what he said were his attempts to destabilize the country after the revolution.
A former aide to Gadhafi told CNN last year that she and his family believe those statements were coerced.
This is one of many serious concerns since 2011 that have emerged about the state of human rights in Libya, where kidnappings, torture and abuse in detention facilities have become commonplace.
"Unfortunately we have seen these confession videos again, this used to be a tactic used by the Gadhafi regime themselves in 2011, during the 2011 conflict we documented numerous cases of these confessions, most likely forced confessions that were taped and shown to a broad audience," Salah said.