UN Secretary General Ban Ki-moon has called on all eligible Afghan voters to cast their ballots in tomorrow's election to help strengthen Afghanistan's democratic institutions.

Voters will elect a president for the second time in Afghanistan's history, and 420 councillors in 34 provinces.

A UN statement says: 'The Secretary General encourages all Afghan women and men eligible to vote to cast their ballots in the upcoming presidential and provincial council elections.

'By participating in these elections, the Afghan people will help Afghanistan strengthen its democratic institutions, bring fresh vigour to the country's political life, and ultimately reaffirm their commitment to contribute to the peace and prosperity of their nation.'

Mr Ban also urged all candidates, their supporters, as well as domestic and international observers, to help 'ensure a smooth and successful electoral process'.

Taliban attacks

In the run-up to the landmark elections, the Taliban has stepped up attacks across Afghanistan.

Security forces killed three gunmen this morning who stormed a bank building in central Kabul.

At least 21 people were killed yesterday and a rocket struck the presidential compound in Kabul.

The attacks followed renewed Taliban threats to sabotage the elections in which 17m Afghans are eligible to vote.

But the NATO-led coalition said that despite a spike in insurgent strikes, less than 1% of polling stations are at risk of being attacked.

Mr Ban also expressed distress over the death of two UN workers in the second deadly suicide attack targeting NATO in Kabul in two days.

Aid efforts

Development organisation Oxfam has said Afghanistan's presidential election should be followed by major reforms in governance to end the 'wasteful' use of foreign aid.

It said too few ordinary Afghans were benefiting from international aid efforts and a third are at risk of hunger.

Oxfam said: 'Aid can make a huge difference in Afghanistan but it has to be well-spent.

'The election of a new government in Kabul must be accompanied by major reforms in governance and aid effectiveness. So far much of the money given by foreign governments is ineffective, uncoordinated or wasteful, and doesn't reach ordinary Afghans.'

The organisation said poverty levels in Afghanistan were among the worst in the world, with many areas facing severe food shortages.

Elsewhere, the UN is holding its first World Humanitarian Day to honour international aid workers.

The event aims to highlight the sacrifices of aid workers and to increase support for their role.

A record 120 international aid workers were killed last year.