Afghan voters formed long lines outside polling stations on Saturday to pick a successor to President Hamid Karzai, with a final turnout expected to exceed 50 per cent - outstripping expectations.
US President Barack Obama congratulated the nation on the ballot - its first democratic transfer of power - and said it was "critical" to its future and securing continued international aid.
"Millions of Afghan men and women took to the polls today with courage and commitment," US Secretary of State John Kerry said in a statement.
"This is their moment. The Afghan people secured this election. They ran this election, and most importantly, they voted in this election."
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There were no major militant attacks during polling, and organisers described the ballot as a huge success, despite
complaints that a shortage of ballot papers had denied some citizens the right to vote.
However, with results not due until April 24 the country faces a testing period, and many Afghans fear a repeat of the fraud scandals that marred the last presidential election in 2009.
If no candidate wins more than 50 per cent in the first round, a run-off is scheduled for late May.
There is no clear favourite among the front-runners to succeed Karzai - former foreign minister Zalmai Rassoul, Abdullah Abdullah, who was runner-up in the 2009 election, and former World Bank academic Ashraf Ghani.
Whoever emerges victorious must lead the fight against the Taliban without the help of US-led combat troops, and also strengthen an economy that currently relies on declining aid money.
"Today's election and massive participation of the people have taken Afghanistan a few steps forward to peace, stability and development," Karzai said in an address to the nation Saturday.
"This was a major effort of the people, our security forces, and all the officials who had a role in holding the election."
The United Nations Security Council also commended "the participation and courage of the Afghan people to cast their ballot despite the threat and intimidation by the Taliban" and other terrorist groups.
Interior Minister Omar Daudzai said late Saturday that four civilians, nine police and seven soldiers had been killed in violence in the past 24-hours, but added that many attacks had been foiled.
The day before the poll, Associated Press photographer Anja Niedringhaus was shot dead by a police commander in eastern Khost province.
She was the third journalist working for international media to be killed during the election campaign, after Swedish journalist Nils Horner and Sardar Ahmad of Agence France-Presse.
