Iranians voted on Friday in a parliamentary election likely to reinforce Supreme Leader Ayatollah Ali Khamenei's power over rival hardliners led by President Mahmoud Ahmadinejad.

Iranian leaders were looking for a high turnout to ease an acute crisis of legitimacy caused by Ahmadinejad's re-election in 2009 when widespread accusations of fraud plunged the Islamic Republic into the worst unrest of its 33-year history.

Iran also faces economic turmoil compounded by Western sanctions over a nuclear program that has prompted threats of military action by Israel, whose leader meets U.S. President Barack Obama in the White House on Monday.

The vote in Iran is only a limited test of political opinion since leading reformist groups stayed out of what became a contest between the Khamenei and Ahmadinejad camps.

"Whenever there has been more enmity towards Iran, the importance of the elections has been greater," Khamenei, 72, said after casting his vote before television cameras.

"The arrogant powers are bullying us to maintain their prestige. A high turnout will be better for our nation ... and for preserving security."

The vote will have scant impact on Iran's foreign or nuclear policies, in which Khamenei already has the final say, but could strengthen the Supreme Leader's hand before the presidential vote next year. Ahmadinejad, 56, cannot run for a third term.

Iranians may be preoccupied with sharply rising prices and jobs, but it is Iran's supposed nuclear ambitions that worry the outside world. Western sanctions over the nuclear program have hit imports, driving prices up and squeezing ordinary Iranians.

OBAMA-NETANYAHU TALKS
Just days away from the talks between Obama and Israeli Prime Minister Benjamin Netanyahu, their aides were scrambling to bridge differences over what Washington fears could be a premature Israeli attack on Iran's nuclear sites.

Netanyahu will press Obama, who is facing a presidential election, to stress publicly the nuclear 'red lines' that Iran must not cross, Israeli officials say.

Global oil prices have spiked to 10-month highs on tensions between the West and Iran, OPEC's second biggest crude producer.

The election took place without the two main opposition leaders. Mirhossein Mousavi and Mehdi Karoubi, who ran for president in 2009, have been under house arrest for more than a year.

Karoubi's website, Sahamnews.org, said opposition groups and political prisoners urged people to shun this 'sham election'.

No independent observers are on hand to monitor the voting or check the turnout figures that officials will announce.

Former president Hashemi Rafsanjani made a pointed reference to the outcome of the 2009 vote, which he questioned at the time.

"If the election outcome turns out to be what the people cast in the ballot boxes, God willing we will have a good parliament," the elder statesman said after voting in Tehran.

State media briefly showed Ahmadinejad voting, apparently making no comment afterward. The outgoing parliament is due to grill him next week on his handling of the economy and other issues - an unprecedented humiliation for an incumbent president, but one he may use to hit back at his foes.

Polling stations opened at 8 am (0430 GMT) and were due to close at 6 pm, but state television said they would stay open longer to cope with the 'extraordinary' turnout.

Ballots are counted manually and Iranians may have to wait three days for full results. Voting was slow at first in affluent northern Tehran but picked up later. Voters queued up in poorer parts of the capital and in provincial cities, Reuters witnesses said.

"I am here to support my establishment against the enemies' plot by voting," said Mahboubeh Esmaili, 28, holding her baby in a queue of about 50 people at a central Tehran polling centre.

SLAP IN FACE
Khamenei has told Iranians that their vote would be a "slap in the face for arrogant powers" such as the United States.

A U.S. official said Iran had clamped down on dissent since the turbulent presidential election nearly three years ago.

"Since then, the regime's repression and persecution of all who stand up for their universal human rights has only intensified," U.S. Under Secretary of State Mario Otero told the United Nations Human Rights Council in Geneva.

The two main groups competing for parliament's 290 seats are the United Front of Principlists, which includes Khamenei loyalists, and the Resistance Front that backs Ahmadinejad.

The president, a blacksmith's son, has long appealed to Iran's rural poor with his humble image and cash handouts from state funds, but spiraling prices have dented his popularity.

Energy and food imports have been hit by sanctions aimed at forcing Iran to halt sensitive nuclear work that the West suspects is a cover for a drive to build atomic bombs. Tehran says it has only peaceful aims, such as generating electricity.

Prices of staple goods, many of them imported, have soared because the Iranian rial's value has sunk as U.S. and European Union sanctions on the financial and oil sectors begin to bite.

Ahmadinejad's critics accuse him of making things worse for low-income Iranians, saying his decision to replace food and fuel subsidies with direct monthly payments since 2010 has fuelled inflation, officially running at around 21 percent.

ALLIES FALL OUT
The president enjoyed solid support from Khamenei in the months of 'Green Movement' protests that followed the 2009 election, but the two men have fallen out badly since then.

For Khamenei, the parliamentary election could reinforce his grip on power against a president seen as trying to undermine the clergy's central role in Iran's complex political hierarchy.

Ahmadinejad and his 'deviant current' allies have alarmed Khamenei's conservative camp by emphasizing nationalist themes of Iranian history and culture over the Islamic ruling system introduced by revolutionary leader Ayatollah Ruhollah Khomeini.

Khamenei succeeded Khomeini, who died in 1989.

Some Iranian media reports said Ahmadinejad hoped to secure the election of his chief of staff, Esfandiar Rahim-Mashaie, to succeed him. Khamenei will want to install one of his own loyalists to prevent further divisions within the ruling elite.

Powerful establishment groups, including senior clerics, the elite Revolutionary Guards and bazaar merchants, formed an alliance to back Khamenei loyalists in the parliamentary vote.

Not everyone can run in Iranian elections. The hardline Guardian Council, made up of six clerics and six jurists who vet candidates, approved more than 3,400 out of 5,382 applicants.

Some politicians said the council barred many established Ahmadinejad supporters, forcing him to pick political unknowns.

The rift between Khamenei and Ahmadinejad broke into the open in April 2011 when the Supreme Leader forced the president to reinstate an intelligence minister he had insisted on firing.

Since then dozens of Ahmadinejad allies have been detained or sacked for links to the "deviant current."

Most strikingly, the president's media adviser, Ali Akbar Javanfekr, has received a one-year jail term for insulting Khamenei, which an appeal court upheld on Wednesday.

The authorities suggested that malign foreign hands were trying to disrupt the election.

"So far, 10 saboteurs who came to Tehran from outside the country have been arrested and are now in detention," Mohammad Taqi Baqeri, a Tehran election official was quoted as saying by the semi-official Fars news agency. He gave no details.