Iranians voted for a new president among a small and heavily vetted field of candidates dominated by hard-line conservatives.
Ultraconservative cleric Ebrahim Raisi is expected to win the June 18 poll easily, after many potential rivals were barred from running by the powerful Guardians Council overseen by Supreme Leader Ayatollah Ali Khamenei.
According to the Interior Ministry, first results are expected on June 19 in afternoon and final results should be released on June 20.
Raisi, 60, heads Iran's judiciary and was one of the judges in 1988 who oversaw a series of speedy trials in which thousands of political prisoners were sentenced to death and executed.
Human rights organizations say he is guilty of crimes against humanity, and the United States has placed him under sanctions.
Analysts have suggested that a win for Raisi would signal the rise of anti-Western hard-liners to the detriment of pragmatists like outgoing two-term President Hassan Rohani, a key architect of the moribund 2015 nuclear deal under which Iran agreed to limit its nuclear program in exchange for sanctions relief.
Both Tehran and Washington have said they want to restore the deal, which was abandoned in 2018 by the administration of former U.S. President Donald Trump. Negotiations to revive the accord restarted in April.
But Khamenei has said that he wants "actions, not promises" from the five world powers who originally signed the accord with Tehran, which has steadily flouted terms of the agreement by rebuilding stockpiles of enriched uranium and increasing its ability to enrich it to higher levels of purity.
At the same time, the Guardians Council, appointed directly by Khamenei, eliminated the vast majority of potential reformist candidates, bolstering Raisi's chances.
Raisi's main challenger is Abdolnaser Hemmati, the only relative moderate left in the race after another moderate candidate quit the race on the last day of the campaign. Two hard-liners also dropped out of the race on the last day, leaving four candidates for voters to choose from.
Hemmati, 64, served as Iran's central bank chief before he was dismissed in order to run for president.
Public opinion polls suggest Hemmati's support is in the single digits even after he gained some momentum late in his campaign by criticizing state restrictions and reaching out to reform-minded Iranians.
Two more hard-liners, Mohsen Rezai, a former commander of the Islamic Revolutionary Guards Corps (IRGC), and Amir Hossein Ghazizadeh Hashemi, who served as parliament's first deputy speaker, remain in the race.
Turnout is being watched closely by observers, who see it as a referendum on the ruling theocracy's handling of a growing number of crises, including an economy hit hard by punitive sanctions reimposed under Trump. Inflation has reached nearly 40 percent and the official unemployment rate stands at 11 percent.
Analysts say the vote could produce the country’s lowest-ever turnout, casting doubts over the popular legitimacy of the winner.
Khamenei has encouraged Iranians to participate in the election, while lashing out at unidentified "enemies" he claims are discouraging people from taking part.
State television reported that in some polling stations voting was extended by two hours -- to 2 a.m. local time on June 19 -- to allow late-comers to cast ballots.
Earlier, state TV had shown long queues outside polling stations in several cities, but RFE/RL's Radio Farda obtained several videos that appeared to show few voters at polling stations in Tehran and other cities. The authenticity of the clips could not be verified.
Contrary to state media reports, one voter who did not give her full name, told Reuters on June 18 that polling stations were "almost empty" in the central Iranian city of Yazd.
A survey conducted by the Iranian Student Polling Agency suggests that only 42 percent of the country’s 59 million registered voters planned to cast ballots. If prediction holds true, it would be a massive decline compared to the 73 percent turnout for Iran's last presidential election in 2017.
The highest turnout for an Iranian presidential election since the Islamic revolution of 1979 that brought the current theocracy to power was 85.2 percent in 2009. The lowest was 50.6 percent in 1993.
Solat Mortazavi, a representative of Raisi's campaign headquarters, said there had been "disruptions" in the voting process at some polling centers in southern Tehran.
But Interior Minister Abdolrahman Fazli said the election was proceeding smoothly at all 70,000 polling stations despite early reports of problems.
Hossein Hassanpour, a deputy police chief in Iran's northern province of Gilan, said 27 people were detained early on June 18 for endangering "the health and security of the elections." He did not provide further details.
Many Iranians have said they will not be voting due to severely restricted choices. They also cited frustration over the economy, state repression, and disillusionment with politicians who have failed to bring change.
“They’re offering five bananas, saying 'Choose any fruit you want,'" one Iranian man complained during a recent open tribune in the central city of Isfahan. "How can you pick an orange from five bananas?”
If no candidate wins an overall majority on June 18, the two with the most votes will go head to head in a second-round runoff.
Despite the attention paid to the election, it is the supreme leader, not the president, who has the last say on Iran’s nuclear and foreign policies.