Libya released all 84 jailed members of the banned Muslim Brotherhood movement who had been held since the late 1990s, Libyan officials said.
"All the 84 members of the Muslim Brotherhood were released today ... amid celebrations in front of the prison in Tripoli in the presence of their families," an official said on condition of anonymity.
"Fivty-five of them have returned home to Benghazi," Libya's second city in the east of the country, the official added.
Libya detained 152 members of the Muslim Brotherhood at the end of the 1990s.
In 2002, two were sentenced to death, 73 to life in prison and 66 were acquitted. The others were sentenced to a 10-year prison term.
The prisoners are charged with violating Law 71, which outlaws political activity opposing the principles of the 1969 revolution in which Libyan leader Moamer Kadhafi took power.
The releases came one month after the New York-based Human Rights Watch (HRW) urged Libyan authorities to free all political prisoners, including the Muslim Brotherhood members who it said numbered 86.