Libyans are going to the polls in the hope of ending the anarchy that has gripped the country since the 2011 overthrow of the Gaddafi regime.
A new 200-seat parliament will be elected in the second poll since the former regime's overthrow.
The UN has described the poll as "an important step in Libya's transition towards stable democratic governance".
The election was called a month ago amid government claims that a renegade general was plotting a coup.
General Khalifa Haftar denied the allegation, but launched a military offensive against Islamist militias whom he accused of holding Libya to ransom.
At least 70 people were killed in the ensuing battles. Gunmen also stormed the parliamentary building in the capital, Tripoli.