The group demanded information about the fate of a Shia imam who went missing in Libya decades ago.
Hannibal Gaddafi appeared in a video aired late on Friday on local Al-Jadeed TV saying anyone who has information about Imam Moussa al-Sadr should come forward.
"I hope that the people who I mean for them to hear me, and they have evidence, to bring out immediately without delay. Because enough of this suffering, enough," Gaddafi said.
"Enough injustice, people here want their son [the imam]."
Gaddafi appeared to have been beaten up and had black eyes but said in the video he is "in good health, happy and relaxed".
He was freed in the city of Baalbek and dispatched to Beirut, the capital, police told the Associated Press news agency.
It was not clear when Gaddafi, who is married to a Lebanese woman, was kidnapped.
The Gaddafi family was long been unwelcomed in Lebanon, especially among members of the Shia Muslim community.
Al-Sadr, one of Lebanon`s most prominent Shia imams in the 20th century, vanished, along with two other people, during a trip to Tripoli in 1978. Lebanon blamed the disappearance on Muammar Gaddafi.
Hannibal, born in 1975, was among a group of family members - including Gaddafi`s wife Safiya, son Mohammed and daughter Aisha - who escaped to neighbouring Algeria after the fall of Tripoli in 2011.
In 2008, he and his Lebanese wife, Aline Skaf, sparked a diplomatic incident with Switzerland when they were arrested in a luxury Geneva hotel for assaulting two former servants.
The Libyan regime demanded that no charges be brought and an apology be made over the allegations that he had assaulted the pair, a Tunisian and a Moroccan. The case was dropped.
Colonel Gaddafi`s son Hannibal freed after Lebanon kidnap
12 December 2015
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The son of late leader Muammar Gaddafi has been freed after being briefly kidnapped by an armed group in Lebanon, security sources say.
