Outgoing President Hamid Karzai has praised Afghans for embracing democracy following a largely peaceful first round of voting for president and local offices that featured a high voter turnout.
In a televised address, Karzai said Afghans had braved bad weather and threats of Taliban violence to cast their ballots.
"The Afghan nation today has put in practice their big jubilee of the nation's participation in voting," Karzai said. "Despite the cold and rainy weather and possible terrorist attack, our sisters and brothers nationwide took in this election and their participation is a step forward and it is a success for Afghanistan."
The vote was a major step in what would be the country's first democratic transfer of power in history.
Despite threats by the Taliban to disrupt the voting, no major attacks were reported. Voting was extended by one hour on April 5 due to a reported heavy turnout and rains.
Afghanistan's election commission chief says preliminary estimates suggest turnout in the elections was 7 million out of 12 million eligible voters, or about 58 percent.
Ahmad Yousuf Nuristani, chairman of the Independent Election Commission, said that by midday some 3.5 million people had cast votes, 36 percent of them women.
Sattar Saadat, head of the Electoral Complaints Commission, told RFE/RL's Radio Free Afghanistan that some complaints of irregularities had already been reported.
"At least 58 complaints were officially recorded an hour ago. We received over 500 complaints over the telephone," Saadat said. "Major complaints came from Wardak, Parwan, Kapisa, Kandahar, and so on. We will look at all of them."
The last presidential election, in 2009, which returned outgoing President Hamid Karzai to office, was marred by widespread fraud and violence.
Interior Minister Omar Daudzai said there had been 140 attacks over 24 hours, leaving nine policemen, seven soldiers, and 89 Taliban killed. He said four civilians were killed and 43 were injured in election-related violence.
WATCH: RFE/RL's Frud Bezhan offers his analysis of the vote from Kabul.
Afghan Interior Ministry spokesman Sidiq Siddiqi said that security forces prevented multiple attempted Taliban attacks.
"The Taliban and the terrorists that kept campaigning against elections and said they will not allow Afghans to participate in the elections, tried their utmost to launch attacks in Nangarhar, Khost, Ghazni and Konar," he said.
"Fortunately, every one of their attempts to intimidate or harm the people was prevented by the Afghan security forces."
Independent Election Commission chief Nuristani said security threats forced officials to close 211 of some 6,000 polling stations.
A shortage of ballots was reported
at some polling stations. "We visited at least seven or eight voting stations to vote, but none of them had ballot papers. People are left in the middle of nowhere. Since 10 or 11 in the morning, people have been waiting for nothing," a man from the northern Baghlan Province told RFE/RL.
Generally, voters said they felt positive as they arrived to cast ballots. Many vowed that Taliban threats could not prevent them from taking part in the election.
WATCH: Afghan voters share hopes for peace, stability.
Many women participated. Hawa Hazrati from Kabul told RFE/RL: "Women's participation was wonderful. The process was transparent, and clean. I am proud of our security forces because they made me feel secure like a new bride."
The U.S. Embassy in Kabul congratulated Afghanistan on the elections, saying in a message on Twitter: "Congratulations to the many Afghans who are voting. You are making the country stronger, and shunning the Taliban."
European Union foreign-policy chief Catherine Ashton was cautiously optimistic.
"This will be a historic moment if we get this right, this democratic transition. We want to see everybody participating, including, I would say, all the women of Afghanistan and we welcome what has been done to try to prepare for these elections," Ashton said.
"The latest information I have, has been that things are going forward and we wait to see now what the results will bring."
Two of the front-runners in the presidential election, Ashraf Ghani and Abdullah Abdullah, commented to the press after casting their ballots.
Ghani, a former finance minister, said the large turnout at polling stations sent a message to the enemies of Afghanistan that their threats cannot intimidate the country's people.
Abdullah, a former foreign minister, called the election "one step forward toward a better future."
After voting at a polling station near the presidential palace, President Hamid Karzai urged his countrymen to go to the polling stations "despite the rain, cold weather, and enemy threats."
"Today is an important day for our future, the future of our country," he added.
Independent Election Commission head Nuristani called on the Afghan people to "prove to the enemies of Afghanistan that nothing can stop them."
Three contenders are expected to dominate the eight-man race to succeed Karzai, who has ruled for 12 years and is constitutionally barred from seeking a third term. Widespread violence, massive fraud and vote-rigging marred Karzai's reelection in 2009.
The front-runners are Ghani and two former foreign ministers, Abdullah and Zalmai Rasul.
The Taliban had threatened to use violence to disrupt Afghanistan's presidential election. But outside of isolated incidents Afghans turned out in large numbers and voted in relative peace. Many displayed their purple fingers -- occasionally the middle one -- as a direct affront to the Taliban.
On the eve of the vote, award-winning German photographer Anja Niedringhaus was killed and Canadian reporter Kathy Gannon was injured when a police officer opened fire on their car in the eastern town of Khost.
The police officer has been arrested. No organization has claimed responsibility.
Niedringhaus is the third journalist working for international media to be killed in Afghanistan during the election campaign.
First Results In Three Weeks
Afghanistan has 12 million eligible voters, and some 200,000 Afghan observers were expected to monitor the vote.
Some international observers pulled out after the Taliban last month attacked a high-security Kabul hotel, where many foreigners, including election monitors, were staying. Nine Afghan and foreign civilians were killed in the attack.
Preliminary results from the first round are expected on April 24 and a final result on May 14, around six weeks after voting day.
With no clear front-runner, it's unlikely that any of the candidates will secure more than the 50 percent of the vote required to win outright. In that case, there will be a runoff between the two leading candidates on May 28.
The transfer of power to a new president is occurring as most Western combat forces are preparing to withdraw from Afghanistan by the end of this year.
With reporting by AP, Reuters, and AFP