At one polling station in the centre of the capital Kabul, only 21 per cent of voters registered cast their ballots.

The election commission's extension of voting by two hours to 5pm local time on Saturday did little to increase turnout.

The low participation was confirmed by local representatives in at least half of Afghanistan's provinces, polling staff and observers.

Poll workers said the main reason for the low turnout was the lack of security.

At least three people were killed and 44 others were injured in election-related explosions or rocket attacks across several provinces and in the capital Kabul.

A third of polling stations remained closed due to security threats in Taliban-controlled areas and other places where the insurgent militia wields influence.

Some 72,000 members of the security forces were deployed to provide security for the election.

Eighteen candidates were on the ballot; four pulled out before election day.

But only incumbent President Ashraf Ghani and chief executive Abdullah Abdullah have a real chance of winning.

According to the election commission, preliminary results are scheduled to be announced on October 19.

Political analyst Ahmad Saeedi predicted that not more than a million people would vote, compared to polls in 2014, when almost 8 million people turned out.

TV station Tolo News quoted unofficial figures by the election commission, saying that fewer than 2 million people voted.

Women in particular appeared to have stayed at home, provincial councils said.

Australian Associated Press