Afghans headed to the polls on Saturday to elect a new President amid high security and threats of violence from Taliban militants, who warned citizens to stay away from polling stations or risk being hurt.

Fear and frustration at the relentless corruption that has characterized successive governments ranks high among the concerns of Afghanistan's 9.6 million eligible voters. The country has also been rattled by an upsurge in violence in the run-up to the elections, following the collapse of US-Taliban talks to end America's longest war.

At some polling stations in the capital of Kabul, voters lined up even before the centers opened, while in other locations election workers had yet to arrive by poll opening time.

Imam Baksh, who works as a security guard, said he wasn't worried about his safety as he stood waiting to mark his ballot, wondering who he would vote for.

'All of them have been so disappointing for our country,' he said.

One of the first reports of violence came from southern Afghanistan, the former spiritual heartland of the Taliban. A bomb attack on a local mosque where a polling station was located wounded 15 people, a doctor at the main hospital in the city of Kandahar said. The doctor spoke on condition of anonymity because he was not authorized to speak with the media.

The wounded included a police officer and several election officials, along with voters. Three were in critical condition.

There were also reports of sporadic rocketing elsewhere in the country, but it wasn't immediately clear if voting sites were the targets.

The leading contenders are incumbent President Ashraf Ghani and his partner in the 5-year-old unity government, Abdullah Abdullah, who already alleges power abuse by his opponent. Cameras crowded both men as they cast their vote in Kabul, with Ghani telling voters they too had a responsibility to call out instances of fraud.

Even in the early hours of voting, complaints had begun to be raised such as polling stations in the capital's posh Wazir Akbar region opening late and biometric machines, aimed at curbing fraud, not working.

In the northern Taimani neighborhood of mostly ethnic Hazaras, two-thirds of the voting registration papers had yet to arrive and angry voters were told their names were not on the list.

Abdul Ghafoor, who spoke on behalf of dozens of men waiting to cast their ballot, said that of about 3,000 registered voters only 400 appeared on the list that had arrived at the center.

Ghafoor said he was told to return at 2 p.m. and that he would be allowed to vote even if his name was not on the list and without using the biometric machine.

'But how can they do this? My vote won't count if I am not on a list,' he said.

In Khoja Ali Mohfaq Herawi mosque in Kabul's well-to-do Shahr-e-Now neighborhood, election workers struggled with biometric machines as well as finding names on voters' lists.

Ahmad Shah, 32, cast his vote, but said the election worker forgot to ink his finger — which is mandatory to prevent multiple voting by the same person.

'What sort of system is this?' he asked, frustrated that he had risked his safety to vote and expressed fear that fraud will mar the election results. 'It's a mess.'

Still, 63-year old Ahmad Khan urged people to vote.

'It is the only way to show the Taliban we are not afraid of them,' he said, though he too worried at the apparent glitches in the process.

Tens of thousands of police, intelligence officials and Afghan National Army personnel have been deployed throughout the country to protect the 4,942 election centers. Authorities said 431 polling centers will stay closed because it was impossible to guarantee their security since they were either in areas under Taliban control or where insurgents could threaten nearby villages.

In Kabul traffic was light, with police and the army scattered throughout the city, stopping cars and looking for anything out of the ordinary. The Taliban said they would take particular aim at Afghanistan's cities.

Outfitted in bullet-proof vests, their rifles by their side, soldiers slowed traffic to a crawl as they searched vehicles. Larger vehicles were not being allowed into the capital on Saturday, which is a usual working day but for the elections was declared a holiday.

Neighbour Pakistan, routinely accused of aiding insurgents, announced it was closing its borders with Afghanistan on Saturday and Sunday to further protect security in the war-weary country.

Campaigning for Saturday's elections was subdued and went into high gear barely two weeks ahead of the polls as most of the 18 presidential candidates expected a deal between the United States and the Taliban to delay the vote. But on September 7, President Donald Trump declared a deal that seemed imminent dead after violent attacks in Kabul killed 12 people, including two US-led coalition soldiers, one of whom was American.

While many of the presidential candidates withdrew from the election, none formally did so, leaving all 18 candidates on the ballot.

Elections in Afghanistan are notoriously flawed and in the last presidential polls in 2014, allegations of widespread corruption were so massive that the United States intervened to prevent violence. No winner was declared and the US cobbled together the unity government in which Ghani and Abdullah shared equal power — Ghani as president and Abdullah as chief executive, a newly created position.

Constant bickering and infighting within the government frustrated attempts to bring in substantive legislation as security, which has been tenuous, continued to deteriorate, frustrating Afghans and causing many to flee as refugees.