Voter turnout in the first round of Afghanistan's presidential election on Saturday may have been as low as 20%, according to preliminary counts, amid threats from the Taliban to attack polling stations.

Afghanistan's Independent Election Commission said data from just over half the country's polling stations showed around 1.1 million people had voted for one of the more than a dozen candidates vying to rule the war-torn country, including the incumbent president, Ashraf Ghani.

If the figures are consistent with the booths yet to report it would indicate that less than a quarter of the country's 9.6 million registered voters cast their ballot on Saturday, a steep decline from the approximately 60% of eligible voters who participated in the 2004 polls. An Afghan official told Reuters the turnout figure could be as low as 20%. This would be the lowest level since the 2001 US-led invasion.

The Afghanistan Analysts Network said there were more than 400 reported attacks causing dozens of casualties across Afghanistan as the country voted, but none were significant enough to have disrupted the polling.