Tunisians are voting to choose a new president, in a decisive final-round vote between two political newcomers: a flamboyant media mogul and a conservative law professor.
Tycoon Nabil Karoui and retired academic Kais Saied swept aside a host of establishment candidates in the first round of voting last month.
Mr Karoui, 56, has campaigned from prison after being arrested on charges of money laundering and tax fraud.
He denies the charges.
Voter turnout was at 17.8% by midday on Sunday, up from 12% at the same time in the first round, the election commission said.
Polls are set to close at 18:00 (17:00 GMT), and official results are expected on Tuesday.
Najwa Salmi, 21, cast her vote at a polling station in northern Tunis, and said she was hoping for “a president who respects his powers”.
“Today I vote to support a candidate who will be president of all Tunisians and be fair,” she told Reuters, without saying who she meant.
Mr Karoui, who was freed by a court order just four days ago, came second in the first round of voting, with 15.6% of the vote to Mr Saied’s 18.4%.
Tunisia’s electoral commission has said that if Mr Karoui loses the run-off he could appeal the result, as he has not been allowed a fair campaign.
What are the two candidates offering?
A 61-year-old law professor nicknamed “the robot”, Mr Saied has run a shrewd and hard campaign, with almost no advertising, on a message of integrity and anti-corruption targeted at young Tunisian voters.
In the week before the polls, he announced that he would not campaign while his rival was in prison.
He has promised electoral reforms, including changes to local elections for regional representatives.
Critics have attacked his conservative social views, however.
In an interview with a local newspaper, he accused foreign powers of encouraging homosexuality in the country.
He is in favour of restoring the death penalty, suspended since 1994 in Tunisia, and has said that if he wins the presidency, his wife will not be the country’s first lady.
As for Mr Karoui, he is dubbed Nabil “Makrouna” (pasta) for his charity’s distribution of money and bags of the staple food.
Supporters view him as a self-made businessman, and praise his philanthropy in a country facing rising living costs and youth unemployment.
He founded the charity to fight poverty – a central theme of his campaign.
Opponents have accused Mr Karoui of using his popular TV station, Nessma, to further his political ambitions.
He was arrested in August on charges of tax evasion and money-laundering shortly before the campaign opened.
The charges have not been dropped, despite his release from prison.
His supporters say powerful forces in Tunisia have conspired to scuttle his candidacy, but authorities say his arrest was based on a three-year-old investigation.
What is the significance of the poll?
The election was brought forward after the death in July of Tunisia’s first democratically elected president, Beji Caid Essebsi.
He took office in 2014, three years after a popular uprising that led to the overthrow of long-serving ruler Zine al-Abidine Ben Ali, and sparked the Arab Spring.
Correspondents says that while the Arab Spring gave Tunisia democracy eight years ago, many believe it brought little else.
And Djordje Todorovic, a foreign observer at the poll, said he was concerned that Tunisia “probably won’t have a strong or stable government after this election”.