Scattered rockets fell on several Afghan cities as polls opened on Thursday for an anxiously awaited presidential election that Taliban fighters have vowed to disrupt with violence.
Shops and businesses were closed and around-the-clock squads of extra police checked the few cars on the streets in Kabul.
In the southern city of Kandahar, a few small rockets landed just before polls opened, provincial governor Tooryalai Wesa said after casting his vote. A Reuters reporter heard two blasts, and two security sources said four people were wounded.
In Kunduz in the north, police detective Abdulrahman Aqtash said two rockets had been fired, one landing near a school used as a polling station. No one was hurt.
Another four rockets were fired in Ghazni province southwest of Kabul, some landing near a polling station. Again, no one was hurt. "About 30 people were gathered there to vote. They all ran away," said Ghazni police chief Khial Baz Sherzai.
President Hamid Karzai was one of the first to vote in an election which could prove the toughest test yet of his own mandate and his nation's fragile democracy.
He cast his ballot under tight security in a polling station at a high school near his presidential palace in Kabul, telling reporters he hoped for victory with an outright majority in a single round.
"One round will be in the interest of the nation," he told reporters, displaying his finger stained with the purple indelible ink meant to help prevent voter fraud.
Asked if he feared violence, he said: "I am not worried."
Karzai faces an unexpectedly strong challenge from his former foreign minister, Abdullah Abdullah. Polls show Karzai winning by a strong margin, but possibly falling short of an outright majority and a second round run-off likely in October.
The president is relying on the endorsements of most of the country's notorious former militia chiefs, raising alarm in the West that warlords could return to power.
The election is also a test for US President Barack Obama, who has ordered a massive troop build-up this year as part of a strategy to reverse Taliban gains.
In a series of statements on Wednesday, the Taliban said they had infiltrated 20 suicide bombers into Kabul and would close all the country's roads, taking no responsibility for the deaths of anyone who defied them to go to the polls.
US officials say there may be some violence, but they do not think it will reach the scale needed to wreck the vote.
The extent of any election violence is hard to predict. The tempo of attacks has clearly increased in the weeks leading to the poll, with fighters mounting two big suicide car-bomb strikes and a building siege inside the normally secure capital.
Security in most of the country is still better than it was in Iraq when several successful elections were held there, but the Taliban may be able to damage the vote, even without big attacks, if their threats keep people from the ballot box.
More than 30,000 US troops have arrived in Afghanistan this year, raising the size of the international force above 100,000 for the first time, including 63,000 Americans.
US General Stanley McChrystal, commander of US and NATO forces in Afghanistan, could ask for more when he issues a report next week.
"The situation is serious and we need to turn the momentum of the enemy, but we can do that," McChrystal told the BBC.
The new troops have made bold advances into previously Taliban-held areas, but have also taken by far the worst casualties of the war. More Western troops have died in Afghanistan since March than in the entire period from 2001-04.
The US military said six Americans died in southern Afghanistan on the eve of the vote. A new poll in the Washington Post found 51 percent of Americans believe the war is not worth fighting, and only a quarter favour sending more troops.
The Afghan government has requested international and domestic media not report violence during polling hours, a ban that the United Nations says it has asked authorities to lift.
Richard Holbrooke, Obama's envoy to Afghanistan and neighbouring Pakistan and currently visiting Kabul, said expectations for the poll's outcome needed to be realistic.
"No election is perfect. Don't expect a perfect election."