Voting has ended in Iran's controversial general election, with the outcome generally expected to be a victory for hardliners.
Khamenei said Iranians must fulfil their duties
Reformists say a conservative comeback is inevitable after some 2,500 pro-reform candidates were disqualified.
A BBC correspondent saw steady voting at several polling stations in Tehran, although nothing like the crowds seen in previous elections.
The United States has criticised the elections as neither free nor fair.
The BBC's Jim Muir in Tehran says voting was brisk in some areas, less so in others.
The results, he says, are keenly awaited, with the reformists themselves predicting that they will suffer a heavy defeat.
Some of their supporters openly called on the people not to turn out - just participating was seen as something of a vote of support for the Islamic system.
Iran's conservative supreme leader Ayatollah Ali Khamenei urged voters to go to the polls, saying Iran's "enemies" wanted a boycott.
Our correspondent says the turnout figures, when they do emerge, will be scrutinised with great interest - indeed, they are currently at the centre of the battle between reformists and hardliners.
Iranian state radio said voting was extended by several hours because of a high turnout.
The final results are not expected for up to a week.
The Guardians Council - the conservative vetting body - deemed many candidates ineligible because of their alleged indifference to Islam and to the constitution, or accused them of questioning the supreme leader's powers.
But critics say the process has become a means by which the Council eliminates rivals.
"Candidates have been barred from participating in the elections in an attempt to limit the choice of the Iranian people for their government," said US State Department spokesman Adam Ereli.
"These actions do not represent free and fair elections and are not consistent with international norms."
The tens of thousands of venues for voting included mosques, desert outposts for nomads and cemeteries for those making the traditional weekly visit to graves.
The biggest of the reform parties, the Participation Front, is not contesting the poll after many of its top members were disqualified.
Other reform factions closer to the centre of the political spectrum did take part, however.
The test for the reformers led by President Mohammad Khatami is whether a disillusioned electorate will support the few factions who are fielding candidates, or turn away from them as traitors, our correspondent says.
The general expectation is that the conservatives will win a majority but still leave moderate reformists with a voice, he adds.
Mr Khatami, described as looking gloomy, voted at the Interior Ministry and told reporters: "This nation has been defeated many times but continued its path and created surprises."
'Traitors to Islam'
On the eve of the election, some of the country's best-known intellectuals and journalists called for a boycott, accusing the hardliners of a widespread clampdown.
But Ayatollah Khamenei told state television in Tehran such people were "against the Iranian nation and the revolution".
Ayatollah Ahmad Jannati, head of the Guardians Council, said those calling for a boycott were "traitors to Islam and their country".
He told worshippers in a Friday prayer sermon, that each ballot cast would be akin to "firing a bullet into the heart of [George] Bush".