Saif al-Islam Gaddafi, second son of the late deposed Libyan leader Col Muammar Gaddafi, has been freed from jail under an amnesty law.
His father’s preferred successor, he had been held by a militia in the town of Zintan for the past six years.
The Abu Bakr al-Siddiq Battalion said he had been released on Friday but he has not been seen in public.
It is feared the move could fuel further instability in Libya.
His lawyer, Khaled al-Zaidi, confirmed he had been released.
He declined to say which city Saif al-Islam had travelled to for security reasons. A source has told the BBC he is in the Tobruk area of eastern Libya.
The Abu Bakr al-Siddiq Battalion said it was acting on a request from the “interim government” based in the east of the country.
However, he has been sentenced to death in absentia by a court in Tripoli, in the west of the country, where control is in the hands of the rival, UN-backed Government of National Accord.
Saif al-Islam is wanted by the International Criminal Court for crimes against humanity during his father’s unsuccessful attempts to put down the rebellion against his rule.
The Zintan Military Council - which had previously been involved in his detention - and Zintan’s municipal council have condemned his release by the Abu Bakr al-Siddiq Battalion.