Abdul-Aziz Al-Hassady said he escaped by snatching a gun from one of the attackers and pointing it at another's head until he was able to get into a car and get away.
He said the attack, which took place Tuesday, reflected the dangers in the Libyan capital, where many armed groups remain outside government control.
The National Transitional Council took control of Libya after the fall of Muammar Qaddafi's regime in August. It has made limited progress in extending its authority and disarming the rebels who fought Qaddafis forces.
On Wednesday, scores of Libyan judges and lawyers protested in the capital against lawless behavior of former rebel groups, who they said should now leave the city and return to their home towns.
The crowd of about 250, carrying placards reading "No to weapons; Yes to justice!" gathered outside Tripoli's courthouse before marching to the central Martyr's Square.
