A soldier of the Libyan Shock troops was kidnapped in Sirte, a military source said.
Soldier Massoud Guma Amari was taken to an unknown destination.
He was on a family visit when he was abducted, the source added.
Libya has been gripped by lawlessness ever since the 2011 overthrow of Muammar Qaddafi and is awash with weapons left over from the NATO-backed uprising against his dictatorship. Rival governments and parliaments dispute power, with swathes of territory in the hands of powerful militia