Afghanistan has begun voting for a new president amid fears of violence and insecurity.

Thousands of Afghans lined up at polling centres in Kabul from early morning on Saturday to cast their ballots.

“This is a very good day for Afghans. People are going to elect their president and provincial council members,” Independent Election Commission chief Yousuf Nooristani said.

“I ask my countrymen to go and vote.”

Abdul Hadi Ghazniwal, 38, standing in a long queue at a voting station, said he was voting for change.

Jamshid Khan, 24, another Kabul resident, said he was somewhat afraid of Taliban threats to disrupt the election but “they can’t stop us, because we have to come here and give a vote”.

The voting began without incident. But insecurity and fraud remain the top concerns for election day, according to officials.

About 12 million voters are eligible to cast ballots at about 6400 polling centres across the country, according to IEC.

Around 400,000 security forces have been deployed.

There are eight presidential candidates, including opposition leader Abdullah Abdullah, former World Bank technocrat Ashraf Ghani and former foreign minister Zalmai Rassoul.

Outgoing president Hamid Karzai, who is barred by the constitution from seeking a third term, cast his ballot at Amani High School, near the presidential palace.

“Today for us, the people of Afghanistan, is a very vital day that will determine our national future. We the people of Afghanistan will elect our provincial council members and our president by our secret votes,” he said, his finger stained with the indelible ink used to prevent people from voting twice.

The three candidates thought to be the front-runners have all promised to sign a security agreement with the United States that will allow thousands of foreign troops to remain in the country after 2014 – which Karzai has refused to do.

The three candidates differ on some issues such as the country’s border dispute with Pakistan. But all preach against fraud and corruption and vow to improve security.

Polls were due to close at 4pm local time.

But a spokesman for the IEC, Noor Mohammad Noor, said polling stations could be kept open on a case-by-case basis to allow everybody in line to vote.

Electoral officials have taken extra measures to prevent fraud after widespread vote-rigging in 2009 marred Karzai’s re-election.

Strict protocols include bar codes on the ballot boxes being delivered to polling centres in all 34 provinces and plans to tally the results immediately after the vote closes.