Kabul  - Amid tight security and militant threats to disrupt polls, the presidential and provincial elections began nationwide Thursday with around 17 million Afghans eligible to vote.

President Hamid Karzai, the frontrunner, is vying for re-election against about 30 candidates including two women. The election is the second direct vote for president in the recent history of Afghanistan.

Former foreign minister Abdullah Abdullah, former finance minister Ashraf Ghani and former planning minister Ramazan Bashardost are the main challengers for the incumbent. All three served in Karzai's government in the past.

Voters are also electing 420 provincial council members for the country's 34 provinces.

More than 270,000 election observers, including 2,000 foreign observers, are overseeing the balloting at more than 6,500 polling centres, while the commission said it was unable to open voting stations in nine districts that remain outside government control.

Polling stations opened at 9:30 am (0500 GMT) and voting is to continue until 4 pm (1130 GMT), while initial results are expected about 48 hours after the polls are closed, according to the Independent Election Commission.

While Karzai leads in recent opinion polls, he is not expected to receive more than 50 per cent to win the elections outright. If no candidate posts a first-round majority, a run-off would be held around first week of October.

Taliban militants vowed to disrupt the vote and have threatened to slit the throats and chop off fingers of anyone who votes on Thursday.

Afghan and NATO military officials offered assurances that more than 100,000 international troops and around 200,000 Afghan forces were on high alert and were prepared to neutralize any attack that might be mounted by the Taliban. (dpa)