Gaddafi was reportedly freed by the Abu Bakr al-Siddiq Battalion militia, which controls the area of Zintan, southwest of the capital of Tripoli.
Gaddafi was captured in Zintan in November 2011, a month after his father was sodomized and killed by rebels.
Gaddafi’s son had been attempting to flee to Niger at the time of his capture. He was sentenced to death in 2015 during a mass trial of former Gaddafi officials in Tripoli.
The Abu Bakr al-Siddiq Battalion released a statement saying he was freed on Friday.
“The citizen Saif al-Islam Muammar al-Qadafi was released in accordance with the law of the General Afwa issued by parliament, the only legitimate authority in the country,” the statement reads.
The Libya Herald reports the release was in response to the Tobruk-based House of Representatives’ amnesty for political prisoners.
Saif al-Islam was the most prominent of Gaddafi’s eight children, al Jazeera reports. He studied at the London School of Economics. He is also wanted by the International Criminal Court for alleged war crimes and crimes against humanity.
His current location is unknown.