Some 54,000 security forces have been deployed to protect polling centres, which open at 7:00 am, but there are concerns the killing of a powerful police chief on Thursday will scare off many voters.
Voting has been delayed in the southern province of Kandahar after a Taliban-claimed attack on a US-Afghan security meeting that killed three people, including General Abdul Raziq.
General Scott Miller, the top US and NATO commander in Afghanistan, escaped injury in the shooting, but 13 others were wounded.
Almost nine million people have registered to vote in the parliamentary election, which is more than three years late and only the third since the fall of the Taliban in 2001.
But the threat of militant attacks and expectations for massive fraud are expected to deter many voters from showing up at the more than 5,000 polling centres.
In the days leading up to the poll, the Taliban has issued several statements urging candidates to withdraw and voters to boycott what the group calls a “malicious American conspiracy”.
Shambolic preparations for the ballot have been made worse by a wave of poll-related violence that has left hundreds dead or wounded.
At least 10 candidates out of more than 2,500 contesting the lower-house election have been killed so far.
The most recent victim was Abdul Jabar Qahraman, who was blown up Wednesday by a bomb placed under his sofa in the southern province of Helmand.
Most of the candidates are political novices and include doctors, mullahs and journalists. Those with the deepest pockets are expected to win.
The United Nations Assistance Mission in Afghanistan, which has spearheaded international efforts to keep Afghan election organisers on track, on Friday urged voters to “exercise their constitutional right to vote”.
The poll is seen as a crucial test for next year s presidential election and an important milestone ahead of a UN meeting in Geneva in November where Afghanistan is under pressure to show progress on “democratic processes”.
But the eleventh hour introduction of biometric voter verification machines, which have never been used in an Afghan election, threatens to derail the process.
Observers are concerned the results could be thrown into turmoil if the devices are broken, lost or destroyed.
There are also fears the data could be manipulated before preliminary results are released on November 10.
Votes cast without the controversial machines will not be counted, the Independent Election Commission has said, even though polling centre workers have received little or no training in how to use them.