Iran on Friday was electing a new parliament in the first nationwide poll since a bitterly contested 2009 vote that returned President Mahmoud Ahmadinejad to power, posing a new test of his support among conservatives.
The elections, to fill the 290 seats in parliament, are being boycotted by Iran's main opposition and reformist groups, the leaders of which have been under house arrest for a year.
Supreme leader Ayatollah Ali Khamenei, casting his ballot moments after polling began, urged a high turnout from the 48-million strong electorate to boost "the future, prestige, security and immunity of the country," according to state television.
The vote was being held amid high international tensions over Iran's controversial nuclear programme, which much of the West fears masks a drive to develop the ability to make atomic weapons.
The United States and Europe have imposed punishing sanctnei framed the poll as part of Iran's showdown with the West, saying: "The arrogant powers, who have been defeated and have been delivered a blow to the mouth, are repeating the issue of sanctions and human rights."
The elections are essentially a struggle between conservatives who back Ahmadinejad and a hardline current that despises him. Each claims stronger fealty than the other to Khamenei.
Unlike in the wake of Ahmadinejad's disputed 2009 victory, no protests were expected in these elections.
But Iran's police chief, Ismail Ahmadi Moghaddam, said security forces were "fully prepared" to counter any problems.
There were no international observers present to watch over the voting, which was scheduled to end at 6:00 pm (1430 GMT) but would almost certainly be extended, based on decisions in previous elections.
The US-based rights group Human Rights Watch said in a statement that the elections were "grossly unfair" because of the opposition boycott and because the the limited list of approved candidates skewed overwhelmingly to conservative regime supporters.
"Iranian authorities have stacked the deck by disqualifying candidates and arbitrarily jailing key members of the reform movement," the group's Middle East director, Joe Stork, was quoted as saying.
The Guardian Council, which vetted the 3,400 candidates allowed to run and which will validate the results, called the idea of foreign observers "an insult to the people" of Iran.
The council's spokesman, Abbas Ali Kadkhodai, predicted on Thursday that "the turnout will be more glorious than in the previous (legislative) elections" in 2008, when turnout of 55 percent was announced by the interior ministry.
Final official results of the elections would be announced Sunions on Iran's economy, driving its currency down and making it increasingly difficult for it to sell its oil.
Israel has threatened military action against Iranian nuclear facilities.
Tehran, which denies it seeks an atomic arsenal, has responded to the pressure and Israeli threat with menaces of its own.
It has said it could close the strategic Strait of Hormuz at the entrance to the Gulf, helping to send global oil prices sharply higher. It has also warned of a "devastating" military response if Israel attacks.
The UN nuclear watchdog, the International Atomic Energy Agency, said last week it "continues to have serious concerns regarding possible military dimensions to Iran's nuclear programme."
IAEA inspectors visited Tehran February 20-21 to try to clear up suspicions, but their requests to see the key military site of Parchin, thought to host blast experiments to design a nuclear warhead, were rebuffed.