Kabul, Aug 18 - The campaigning for the Aug 20 presidential elections in Afghanistan ended Monday with top candidates addressing rallies attended by thousands of cheering supporters, a media report said.

About 17 million people will vote Thursday to elect a president for the second time in Afghanistan's history. They will also elect 420 councilors in 34 provinces, The News reported.

President Hamid Karzai, who has ruled Afghanistan since the US-led invasion overthrew the Taliban regime in 2001, is the front-runner but a strong campaign by former foreign minister Abdullah Abdullah could force a run-off.

More than 10,000 people poured into a Kabul stadium - a once notorious Taliban execution ground - wearing blue baseball hat waving blue flags, carrying pictures of Abdullah and chanting his name over and over again.

In a vote stunt rare for Afghanistan, a helicopter circled overhead, dropping hundreds of leaflets with Abdullah's photo, election sign and number as marked on the ballot paper to help the illiterate majority vote.

Afghan police later arrested the pilots of two helicopters and campaign staff for allegedly violating Kabul airspace by dropping the leaflets.

'Hey compatriots, wake up, it is time for a big change,' said the leaflets written in the three most common Afghan languages, Dari, Pashtu and Uzbeki.

Karzai, whose office said eight candidates have now abdicated in his favour, leaving around 30 contenders in the fray, came under fire for alliances with warlords during first television debate attended by an Afghan head of state.