The Taliban's and other insurgent leaders could stand as candidates in Afghanistan's next presidential election, to be held in April 2014, the country's top poll official said Wednesday.

President Hamid Karzai, who is serving his second term as leader of the war-torn nation, is constitutionally barred from running in the election and no clear candidate to succeed him has yet emerged.

The vote, scheduled for April 5, 2014, is seen as crucial to Afghan stability after the withdrawal of NATO troops and Fazil Ahmad Manawi, the head of the Independent Election Commission (IEC) insisted his body would act impartially.

"We are even prepared to pave the ground for the armed opposition, be it the Taliban or Hezb-i-Islami, to participate in the election, either as voters or candidates," Manawi told a news conference.

"There will be no discrimination," the IEC chief added, defending the body in response to a question about its impartiality.

Hezb-i-Islami is the faction of former prime minister Gulbuddin Hekmatyar which wages an insurgency along with the Taliban against Karzai's Western-backed government.

Under the IEC timetable, initial results of the ballot will be announced on April 24 and final results on May 14, with May 28 set aside for any potential run-off vote. Provincial council elections will be held at the same time as the main poll.

The 2009 poll, in which Karzai was reelected over former foreign minister Abdullah Abdullah, was marred by widespread allegations of fraud, and the credibility of the 2014 vote is seen as key to avoiding an escalation in violence after the NATO withdrawal.

Donor nations at a conference in Tokyo in July pledged $16 billion for Afghanistan to prevent the country from sliding back into turmoil when foreign combat troops depart, with several pre-conditions including presidential elections in 2014.

The International Crisis Group think-tank warned this month that the Kabul government could fall apart after NATO troops withdraw, particularly if the presidential elections are affected by fraud.

The Taliban, whose hardline Islamist regime was overthrown in 2001 by a US-led invasion for harbouring Osama bin Laden, did not take part in the 2009 election, instead launched polling day attacks that killed more than 20 people.

Security officials said they were confident they would learn lessons from 2009 as they seek to prevent violence in the run-up to the next election, only the third since the fall of the Taliban.

"Afghan security institutions will start working to design a comprehensive plan for security of election," defence ministry chief of staff Shir Mohammad Karimi said.

Under the Afghan system, voters elect the president as an individual rather than as a representative of a party, and candidates must submit their nominations by October 6, 2013.

The IEC will then rule on their admissibility and publish a final list of candidates on November 16.